{"id":546,"date":"2025-11-30T16:04:51","date_gmt":"2025-11-30T08:04:51","guid":{"rendered":"https:\/\/www.xgnd.net\/?p=546"},"modified":"2025-11-30T16:05:32","modified_gmt":"2025-11-30T08:05:32","slug":"%e3%80%8c%e5%81%9a%e9%a2%98%e7%ac%94%e8%ae%b0%e3%80%8d%e6%a0%91%e4%b8%8a%e8%83%8c%e5%8c%85","status":"publish","type":"post","link":"https:\/\/www.xgnd.net\/index.php\/2025\/11\/30\/%e3%80%8c%e5%81%9a%e9%a2%98%e7%ac%94%e8%ae%b0%e3%80%8d%e6%a0%91%e4%b8%8a%e8%83%8c%e5%8c%85\/","title":{"rendered":"\u300c\u505a\u9898\u7b14\u8bb0\u300d\u6811\u4e0a\u80cc\u5305"},"content":{"rendered":"<p>\u8fd9\u7c7b\u9898\u611f\u89c9\u76f8\u5bf9\u662f\u6bd4\u8f83\u5957\u8def\u7684\uff0c\u4f46\u5b9e\u9645\u5199\u8d77\u6765\u5751\u70b9\u6bd4\u8f83\u591a\uff0c\u5982\u9700\u8981\u63a7\u5236\u597d\u679a\u4e3e\u7684\u4e0a\u4e0b\u754c\uff0c\u4ee5\u53ca\u8981\u8003\u8651\u65b0\u72b6\u6001\u662f\u5426\u4f1a\u88ab\u8986\u76d6\u7b49\u95ee\u9898\u3002<\/p>\n<p>\u4e00\u822c\u6765\u8bf4\uff0c\u5927\u591a\u6570\u6811\u4e0a\u80cc\u5305\u90fd\u662f 01 \u80cc\u5305\uff0c\u56e0\u6b64\u8f6c\u79fb\u65f6\u8981\u6ce8\u610f\u597d\u5185\u5916\u5c42\u5faa\u73af\u679a\u4e3e\u7684\u65b9\u5411\uff0c\u4ee5\u53ca\u786e\u4fdd\u65b0\u72b6\u6001\u4e0d\u88ab\u8986\u76d6\u548c\u4e0d\u4f1a\u91cd\u590d\u8003\u8651\uff0c\u4e3a\u4e86\u907f\u514d\u4e0a\u9762\u7684\u60c5\u51b5\u901a\u5e38\u53ef\u4ee5\u4f7f\u7528\u4e00\u4e2a tmp \u6570\u7ec4\u5c06\u7b54\u6848\u6682\u5b58\u4e0b\u6765\uff0c\u8f6c\u79fb\u5b8c\u518d\u5bf9 dp \u6570\u7ec4\u8fdb\u884c\u66f4\u65b0\uff08\u4e5f\u53ef\u4ee5\u8f6c\u79fb\u524d\u5c31\u5b58\u4e0b\u6765\uff09\u3002<\/p>\n<p>\u6b64\u7c7b\u95ee\u9898\u7684\u590d\u6742\u5ea6\u4e00\u822c\u662f $\\mathcal{O}(n^2)$\uff0c\u76f4\u89c2\u7406\u89e3\u662f\u56e0\u4e3a\u4efb\u610f\u4e24\u4e2a\u70b9\u53ea\u4f1a\u5728\u5176 lca \u5904\u5339\u914d\u4e00\u6b21\uff0c\u6240\u4ee5\u662f $\\mathcal{O}(n^2)$\u3002\u8981\u4fdd\u8bc1\u590d\u6742\u5ea6\u7684\u6b63\u786e\u6027\uff0c\u8fd8\u8981\u6ce8\u610f\u63a7\u5236 dp \u679a\u4e3e\u7684\u4e0a\u4e0b\u754c\uff0c\u5982\u679c\u6ca1\u63a7\u5236\u597d\uff0c\u53ef\u80fd\u4f1a\u88ab\u4e00\u6761\u94fe\u7684\u6570\u636e\u5361\u5230 $\\mathcal{O}(n^3)$\u3002<\/p>\n<p>\u672c\u6587\u4e2d\u7edf\u4e00\u7528 $x$ \u8868\u793a\u5f53\u524d\u8282\u70b9\uff0c$to$ \u8868\u793a\u5176\u513f\u5b50\u8282\u70b9\u3002<\/p>\n<h3><a href=\"https:\/\/www.luogu.com.cn\/problem\/P2015\">\u4e8c\u53c9\u82f9\u679c\u6811<\/a><\/h3>\n<p>\u4e00\u9053\u6a21\u677f\u9898\u3002\u8bbe $dp[x][i]$ \u8868\u793a\u8868\u793a $x$ \u7684\u5b50\u6811\u5185\u4fdd\u7559 $i$ \u6761\u8fb9\uff0c\u81f3\u591a\u4fdd\u7559\u7684\u82f9\u679c\u6570\u76ee\u3002\u4e0d\u96be\u53d1\u73b0\uff0c\u5982\u679c\u6211\u4eec\u60f3\u8981\u4fdd\u7559\u4e00\u6761\u8fb9\uff0c\u90a3\u4e48\u5fc5\u987b\u4fdd\u7559\u4ece\u6839\u8282\u70b9\u5230\u8fd9\u6761\u8fb9\u8def\u5f84\u4e0a\u7684\u6240\u6709\u8fb9\uff0c\u6240\u4ee5\u53ef\u4ee5\u5f97\u51fa\u72b6\u6001\u8f6c\u79fb\u65b9\u7a0b\uff1a<\/p>\n<p>$$dp[x][i]=max(dp[x][i],dp[x][i-j-1]+dp[to][j]+v)$$<\/p>\n<p>\u5176\u4e2d $i-j-1$ \u800c\u4e0d\u662f $i-j$ \u6b63\u662f\u56e0\u4e3a\u6211\u4eec\u5fc5\u987b\u8981\u4fdd\u7559\u5f53\u524d\u5230\u513f\u5b50\u7684\u8fb9\u624d\u80fd\u8fde\u5230\u5b50\u6811\u5185\u7684\u8fb9\u3002<\/p>\n<p>code\uff1a<\/p>\n<pre><code class=\"language-cpp\">#include &amp;lt;bits\/stdc++.h&amp;gt;\nusing namespace std;\ntypedef long long ll;\nconst int maxn = 150, mod = 1e9 + 7, INF = 1e9;\nvector&amp;lt;pair&amp;lt;int,int&amp;gt;&amp;gt; g[maxn];\nint dp[maxn][maxn];\nint siz[maxn];\nint n,m;\n\nvoid dfs(int x,int fa){\n    for(auto &amp;amp;[to,v]:g[x]){\n        if(to==fa)continue;\n        dfs(to,x);\n        siz[x]+=siz[to]+1;\n        for(int i=min(siz[x],m);i&amp;gt;=0;i--){\n            for(int j=min(siz[to],i-1);j&amp;gt;=0;j--){\n                dp[x][i]=max(dp[x][i],dp[x][i-j-1]+dp[to][j]+v);\n            }\n        }\n    }\n}\n\nvoid solve(){\n    cin&amp;gt;&amp;gt;n&amp;gt;&amp;gt;m;\n\n    for(int i=1;i&amp;lt;n;i++){\n        int x,y,v;\n        cin&amp;gt;&amp;gt;x&amp;gt;&amp;gt;y&amp;gt;&amp;gt;v;\n        g[x].push_back({y,v});\n        g[y].push_back({x,v});\n    }\n    dfs(1,0);\n    cout&amp;lt;&amp;lt;dp[1][m]&amp;lt;&amp;lt;&amp;#039;\\n&amp;#039;;\n}\n\nsigned main() {\n    ios::sync_with_stdio(0);\n    int t = 1;\n    \/\/ cin&amp;gt;&amp;gt;t;\n    while (t--) {\n        solve();\n    }\n\n    return 0;\n}<\/code><\/pre>\n<h3><a href=\"https:\/\/www.luogu.com.cn\/problem\/P1273\">\u6709\u7ebf\u7535\u89c6\u7f51<\/a><\/h3>\n<p>\u8bbe $dp[x][i]$ \u8868\u793a\u5728\u4ee5 $x$ \u4e3a\u6839\u7684\u5b50\u6811\u5185\u9009\u53d6 $i$ \u4e2a\u53f6\u5b50\u8282\u70b9\uff08\u7528\u6237\uff09\u80fd\u591f\u83b7\u5f97\u7684\u6700\u5927\u4ef7\u503c\u3002<\/p>\n<p>\u4e0d\u90a3\u5f97\u51fa\u72b6\u6001\u8f6c\u79fb\u65b9\u7a0b<\/p>\n<p>$$dp[x][i]=max(dp[x][i],dp[x][i-j]+dp[to][j]-w)$$<\/p>\n<p>\u521d\u59cb\u5316\u53f6\u5b50\u8282\u70b9\u7684\u72b6\u6001 $dp[x][1] = a[x]$ \u5373\u53ef\u3002<\/p>\n<pre><code class=\"language-cpp\">#include&amp;lt;bits\/stdc++.h&amp;gt;\nusing namespace std;\nconst int inf=-0x3f3f3f3f;\nconst int maxn=3005;\nint n,m;\nvector&amp;lt;pair&amp;lt;int,int&amp;gt;&amp;gt; g[maxn];\nint dp[maxn][maxn];\nint a[maxn];\nint siz[maxn];\n\nvoid dfs(int x){\n    if(g[x].size()==0){\n        dp[x][1]=a[x-n+m];\n        siz[x]=1;\n        return;\n    }\n    for(auto &amp;amp;[to,w]:g[x]){\n        dfs(to);\n        siz[x]+=siz[to];\n        for(int j=siz[x];j&amp;gt;=0;j--){\n            for(int k=0;k&amp;lt;=min(siz[to],j);k++){\n                dp[x][j]=max(dp[x][j],dp[x][j-k]+dp[to][k]-w);\n            }\n        }\n    }\n}\n\nint main(){\n    ios::sync_with_stdio(0);\n    memset(dp,inf,sizeof(dp));\n    cin&amp;gt;&amp;gt;n&amp;gt;&amp;gt;m;\n\n    for(int i=1;i&amp;lt;=n-m;i++){\n        int k,x,v;\n        cin&amp;gt;&amp;gt;k;\n        for(int j=1;j&amp;lt;=k;j++){\n            cin&amp;gt;&amp;gt;x&amp;gt;&amp;gt;v;\n            g[i].push_back({x,v});\n        }\n    }\n    for(int i=1;i&amp;lt;=m;i++){\n        cin&amp;gt;&amp;gt;a[i];\n    }\n    for(int i=1;i&amp;lt;=n;i++)dp[i][0]=0;\n    dfs(1);\n    for(int i=m;i&amp;gt;=0;i--){\n        if(dp[1][i]&amp;gt;=0){\n            cout&amp;lt;&amp;lt;i&amp;lt;&amp;lt;endl;\n            return 0;\n        }\n    }\n    return 0;\n}<\/code><\/pre>\n<h3><a href=\"https:\/\/www.luogu.com.cn\/problem\/P3177\">\u6811\u4e0a\u67d3\u8272<\/a><\/h3>\n<p>\u6ce8\u610f\u5230\uff0c\u6bcf\u4e00\u6761\u8fb9\u7684\u88ab\u8def\u5f84\u7ecf\u8fc7\u7684\u6b21\u6570\u4e3a\u8fb9\u4e24\u4fa7\u540c\u8272\u70b9\u4e2a\u6570\u7684\u4e58\u79ef\uff0c\u5373 <\/p>\n<p>$$cnt=(siz[to]-m)<em>(n-k-siz[to]+m)+m<\/em>(k-m)$$<\/p>\n<p>\u5176\u4e2d $siz[to]$ \u8868\u793a\u5b50\u6811\u5927\u5c0f\uff0c$m$ \u8868\u793a\u5b50\u6811\u5185\u9009\u7684\u9ed1\u70b9\u6570\u3002\u90a3\u4e48\u6bcf\u4e00\u6761\u8fb9\u7684\u8d21\u732e\u5c31\u662f $cnt*w$\u3002<\/p>\n<p>\u8bbe $dp[x][i]$ \u8868\u793a\u5728\u4ee5 $x$ \u4e3a\u6839\u7684\u5b50\u6811\u5185\u9009\u53d6 $i$ \u4e2a\u70b9\u67d3\u6210\u9ed1\u8272\u7684\u6700\u5927\u6536\u76ca\u3002\u4e8e\u662f\u5f97\u5230\u72b6\u6001\u8f6c\u79fb\u65b9\u7a0b\u4e3a<\/p>\n<p>$$dp[x][i]=max(dp[x][i],dp[x][i-m]+dp[to][m]+cnt*w)$$<\/p>\n<p>\u6ce8\u610f\u8fd9\u9898\u8981\u4e0a\u4e0b\u754c\u4f18\u5316\uff0c\u4e0d\u7136\u4f1a\u88ab\u4e00\u6761\u94fe\u7684\u6570\u636e\u5361\u3002<\/p>\n<pre><code class=\"language-cpp\">#include&amp;lt;bits\/stdc++.h&amp;gt;\nusing namespace std;\ntypedef long long ll;\nconst int maxn=2005,INF=0x3f3f3f3f;\nint _;\nint n,k;\nvector&amp;lt;pair&amp;lt;int,int&amp;gt;&amp;gt; g[maxn];\nll dp[maxn][maxn];\nint siz[maxn];\n\nvoid dfs(int x,int fa){\n    siz[x]=1;\n    dp[x][0]=dp[x][1]=0;\n    for(auto &amp;amp;[to,w]:g[x]){\n        if(to==fa)continue;\n        dfs(to,x);\n        siz[x]+=siz[to];\n        for(int i=min(k,siz[x]);i&amp;gt;=0;i--){ \n            for(int m=max(0,i-siz[x]+siz[to]);m&amp;lt;=min(i,siz[to]);m++){\n                if(dp[x][i-m]==-1)continue;\n                dp[x][i]=max(dp[x][i],dp[x][i-m]+dp[to][m]+1ll*(n-k-siz[to]+m)*(siz[to]-m)*w+1ll*(k-m)*m*w);\n            }\n        }\n    }\n}\n\nint main(){\n    ios::sync_with_stdio(0);\n    memset(dp,-1,sizeof dp);\n    cin&amp;gt;&amp;gt;n&amp;gt;&amp;gt;k;\n\n    for(int i=1;i&amp;lt;n;i++){\n        int x,y,z;\n        cin&amp;gt;&amp;gt;x&amp;gt;&amp;gt;y&amp;gt;&amp;gt;z;\n        g[x].push_back({y,z});\n        g[y].push_back({x,z});\n    }\n\n    dfs(1,0);\n\n    cout&amp;lt;&amp;lt;dp[1][k]&amp;lt;&amp;lt;&amp;#039;\\n&amp;#039;;\n\n    return 0 ^ _ ^ 0;\n}<\/code><\/pre>\n<h3><a href=\"https:\/\/www.luogu.com.cn\/problem\/P1272\">\u91cd\u5efa\u9053\u8def<\/a><\/h3>\n<p>\u8bbe $dp[x][i]$ \u8868\u793a\u5728\u4ee5 $x$ \u4e3a\u6839\u7684\u5b50\u6811\u5185\uff0c\u83b7\u5f97\u5927\u5c0f\u4e3a $i$ \u7684\u5b50\u6811\u6240\u9700\u8981\u5220\u9664\u7684\u8fb9\u7684\u4e2a\u6570\u3002<\/p>\n<p>\u5f53\u6211\u4eec\u60f3\u83b7\u5f97\u5927\u5c0f\u4e3a 1 \u7684\u5b50\u6811\u65f6\u53ea\u9700\u8981\u5c06\u513f\u5b50\u8282\u70b9\u7684\u8fde\u8fb9\u5220\u6389\u5373\u53ef\uff0c\u4e8e\u662f\u53ef\u4ee5\u521d\u59cb\u5316<\/p>\n<p>$$<br \/>\ndp[x][1]=<br \/>\n\\left{<br \/>\n\\begin{aligned}<br \/>\n&amp;g[x].size(),x\u4e3a\u6839\\<br \/>\n&amp;g[x].size()-1,x\u4e0d\u4e3a\u6839\\<br \/>\n\\end{aligned}<br \/>\n\\right.$$<\/p>\n<p>$g[x].size()$ \u8868\u793a\u70b9 $x$ \u7684\u5ea6\u6570\uff0c\u6ce8\u610f\u5728\u6839\u5904\u9700\u8981\u7279\u5224\u3002<\/p>\n<p>\u56e0\u4e3a\u5728\u521d\u59cb\u5316\u7684\u65f6\u5019\u5c31\u5df2\u7ecf\u5c06\u513f\u5b50\u8282\u70b9\u7684\u8fde\u8fb9\u5220\u6389\u4e86\uff0c\u6240\u4ee5\u5f53\u5b50\u8282\u70b9\u5411\u7236\u8282\u70b9\u8f6c\u79fb\u65f6\uff0c\u82e5\u9009\u62e9\u4e0e\u7236\u8282\u70b9\u76f8\u8fde\uff0c\u9700\u8981\u5c06\u8fd9\u6761\u5220\u6389\u7684\u8fb9\u52a0\u56de\u6765\uff0c\u6216\u8005\u8bf4\u662f\u5c06\u5220\u9664\u7684\u8fb9\u7684\u4e2a\u6570\u51cf\u4e00\uff0c\u4e8e\u662f\u53ef\u4ee5\u5f97\u5230\u4ee5\u4e0b\u72b6\u6001\u8f6c\u79fb\u65b9\u7a0b<\/p>\n<p>$$dp[x][i+j]=min(dp[x][i+j],dp[x][i]+dp[to][j]-1)$$<\/p>\n<p>\u6ce8\u610f\u6bcf\u68f5\u5b50\u6811\u66f4\u65b0\u5b8c\u540e\u90fd\u8981\u66f4\u65b0\u4e00\u6b21\u5168\u5c40\u7b54\u6848\uff0c\u66f4\u65b0\u65f6\u6ce8\u610f\u5b50\u6811\u5fc5\u987b\u8981\u4e0e\u7236\u8282\u70b9\u65ad\u5f00\u3002<\/p>\n<pre><code class=\"language-cpp\">#include &amp;lt;bits\/stdc++.h&amp;gt;\nusing namespace std;\ntypedef long long ll;\n#define int ll\nconst int maxn=5050,mod=998244353,INF=1e9;\nvector&amp;lt;int&amp;gt; g[maxn];\nint dp[maxn][maxn];\nint siz[maxn];\nint ans;\nint m;\n\nvoid dfs(int x,int fa){\n    dp[x][0]=0;\n    if(x==1)dp[x][1]=g[x].size();\n    else dp[x][1]=g[x].size()-1;\n    siz[x]=1;\n    for(int to:g[x]){\n        if(to==fa)continue;\n        dfs(to,x);\n        for(int i=siz[x];i&amp;gt;=1;i--){\n            for(int j=1;j&amp;lt;=siz[to];j++){\n                dp[x][i+j]=min(dp[x][i+j],dp[x][i]+dp[to][j]-1);\n            }\n        }\n        siz[x]+=siz[to];\n    }\n    if(x==1)ans=min(ans,dp[x][m]);\n    else ans=min(ans,dp[x][m]+1);\n}\n\nvoid solve(){\n    int n;\n    cin&amp;gt;&amp;gt;n&amp;gt;&amp;gt;m;\n\n    for(int i=1;i&amp;lt;n;i++){\n        int x,y;\n        cin&amp;gt;&amp;gt;x&amp;gt;&amp;gt;y;\n        g[x].push_back(y);\n        g[y].push_back(x);\n    }\n\n    for(int i=1;i&amp;lt;=n;i++){\n        for(int j=1;j&amp;lt;=n;j++){\n            dp[i][j]=INF;\n        }\n    }\n\n    ans=INF;\n\n    dfs(1,0);\n    cout&amp;lt;&amp;lt;ans&amp;lt;&amp;lt;&amp;#039;\\n&amp;#039;;\n}\n\nsigned main(){\n    ios::sync_with_stdio(0);\n    int t=1;\n    \/\/ cin&amp;gt;&amp;gt;t;\n    while(t--){\n        solve();\n    }\n\n    return 0;\n}<\/code><\/pre>\n<h3><a href=\"https:\/\/atcoder.jp\/contests\/abc287\/tasks\/abc287_f\">Components<\/a><\/h3>\n<p>\u4f9d\u7136\u662f\u6811\u4e0a\u80cc\u5305\uff0c\u8003\u8651\u4ece\u513f\u5b50\u5411\u7236\u4eb2\u8f6c\u79fb\u65f6\u662f\u5426\u80fd\u591f\u5f62\u6210\u4e00\u4e2a\u8fde\u901a\u5757\uff0c\u90a3\u4e48\u6211\u4eec\u5fc5\u987b\u77e5\u9053\u513f\u5b50\u8282\u70b9\u662f\u5426\u88ab\u9009\u5728\u67d0\u4e2a\u8fde\u901a\u5757\u4e2d\uff0c\u4e8e\u662f\u6211\u4eec\u53ef\u4ee5\u8bbe $dp[u][i][0\/1]$ \u8868\u793a\u4ee5 $x$ \u4e3a\u6839\u7684\u5b50\u6811\uff0c\u5b50\u6811\u91cc\u9762\u603b\u5171\u9009 $i$ \u4e2a\u8fde\u901a\u5757\uff0c$x$ \u81ea\u5df1\u9009\u4e0d\u9009\uff0c\u7684\u65b9\u6848\u6570\u6709\u591a\u5c11\u3002\u6211\u4eec\u53ef\u4ee5\u5206\u4e09\u79cd\u60c5\u51b5\u8ba8\u8bba\u3002<\/p>\n<p>\u82e5 $x$ \u4e0d\u9009\uff0c $to$ \u9009\u4e0d\u9009\u90fd\u884c\uff0c\u5c31\u6709<\/p>\n<p>$$dp[x][i+j][0]+=dp[x][i][0]*(dp[to][j][0]+dp[to][j][1])$$<\/p>\n<p>\u82e5 $x$ \u9009\uff0c $to$ \u4e0d\u9009\uff0c\u5c31\u6709<\/p>\n<p>$$dp[x][i+j][1]+=dp[x][i][1]*dp[to][j][0]$$<\/p>\n<p>\u82e5 $x$ \u9009\uff0c $to$ \u4e5f\u9009\uff0c\u4e24\u8005\u4f1a\u5f62\u6210\u4e00\u4e2a\u8fde\u901a\u5757\uff0c\u4f7f\u5f97\u603b\u8fde\u901a\u5757\u4e2a\u6570\u51cf\u4e00\uff0c\u5c31\u6709<\/p>\n<p>$$dp[x][i+j-1][1]+=dp[x][i][1]*dp[to][j][1]$$<\/p>\n<pre><code class=\"language-cpp\">#include &amp;lt;bits\/stdc++.h&amp;gt;\nusing namespace std;\ntypedef long long ll;\n#define int ll\nconst int maxn=5050,mod=998244353,INF=1e9;\nvector&amp;lt;int&amp;gt; g[maxn];\nint dp[maxn][maxn][2];\nint siz[maxn];\nint n;\n\nvoid dfs(int x,int fa){\n    dp[x][0][0]=dp[x][1][1]=1;\n    siz[x]=1;\n    for(int to:g[x]){\n        if(to==fa)continue;\n        dfs(to,x);\n        for(int i=siz[x];i&amp;gt;=0;i--){\n            for(int j=siz[to];j&amp;gt;=1;j--){\n                (dp[x][i+j][0]+=dp[x][i][0]*(dp[to][j][0]+dp[to][j][1])%mod)%=mod;\n                if(i==0)continue;\n                (dp[x][i+j][1]+=dp[x][i][1]*dp[to][j][0]%mod)%=mod;\n                (dp[x][i+j-1][1]+=dp[x][i][1]*dp[to][j][1]%mod)%=mod;\n            }\n        }\n        siz[x]+=siz[to];\n    }\n}\n\nvoid solve(){\n    cin&amp;gt;&amp;gt;n;\n\n    for(int i=1;i&amp;lt;n;i++){\n        int x,y;\n        cin&amp;gt;&amp;gt;x&amp;gt;&amp;gt;y;\n        g[x].push_back(y);\n        g[y].push_back(x);\n    }\n\n    dfs(1,0);\n\n    for(int i=1;i&amp;lt;=n;i++){\n        cout&amp;lt;&amp;lt;(dp[1][i][1]+dp[1][i][0])%mod&amp;lt;&amp;lt;&amp;#039;\\n&amp;#039;;\n    }\n}\n\nsigned main(){\n    ios::sync_with_stdio(0);\n    int t=1;\n    \/\/ cin&amp;gt;&amp;gt;t;\n    while(t--){\n        solve();\n    }\n\n    return 0;\n}<\/code><\/pre>\n<h3><a href=\"https:\/\/atcoder.jp\/contests\/abc207\/tasks\/abc207_f\">Tree Patrolling<\/a><\/h3>\n<p>\u4e00\u70b9\u8282\u70b9\u4f1a\u51fa\u73b0\u4e09\u79cd\u60c5\u51b5\uff1a\u4e0d\u88ab\u5b88\u536b\uff0c\u6ca1\u4eba\u4f46\u88ab\u5b88\u536b\uff0c\u6709\u4eba\u3002\u5e76\u4e14\u8fd9\u4e09\u79cd\u60c5\u51b5\u90fd\u4f1a\u5f71\u54cd\u6211\u4eec dp \u7684\u8f6c\u79fb\uff0c\u6240\u4ee5\u5728\u8bbe\u8ba1 dp \u72b6\u6001\u65f6\u5c31\u9700\u8981\u5c06\u4ed6\u4eec\u8003\u8651\u8fdb\u53bb\u3002<\/p>\n<p>\u4e8e\u662f\u6211\u4eec\u53ef\u4ee5\u8bbe $dp[x][i][3]$ \u8868\u793a\u5728\u4ee5 $x$ \u4e3a\u6839\u7684\u5b50\u6811\u5185\uff0c\u6709 $i$ \u4e2a\u8282\u70b9\u88ab\u5b88\u536b\uff0c$x$ \u81ea\u5df1\u4e0d\u88ab\u5b88\u536b\u6216\u6ca1\u4eba\u4f46\u88ab\u5b88\u536b\u6216\u6709\u4eba\u7684\u65b9\u6848\u6570\u3002\u5206\u4e09\u79cd\u60c5\u51b5\u8ba8\u8bba\u3002<\/p>\n<p>\u82e5 $x$ \u4e0d\u88ab\u5b88\u536b\uff0c\u90a3\u4e48 $to$ \u6ca1\u6709\u4eba\u5c31\u884c\u3002<\/p>\n<p>$$dp[x][i+j][0]+=dp[x][i][0]*(dp[to][j][0]+dp[to][j][1])$$<\/p>\n<p>\u82e5 $x$ \u6ca1\u4eba\u4f46\u88ab\u5b88\u536b\uff0c\u6b64\u65f6\u53c8\u6709\u4e24\u79cd\u60c5\u51b5\uff1a\u7b2c\u4e00\u79cd\u662f\u6b64\u524d $x$ \u5c1a\u672a\u88ab\u5b88\u536b\uff0c\u76f4\u5230 $to$ \u6709\u4eba\u540e $x$ \u624d\u88ab\u5b88\u536b\uff1b\u7b2c\u4e8c\u79cd\u662f\u6b64\u524d $x$ \u5df2\u7ecf\u88ab\u5b88\u536b\uff0c\u6ce8\u610f\u6b64\u65f6\u88ab\u5b88\u536b\u7684\u8282\u70b9\u6570\u591a\u4e00\u3002<\/p>\n<p>$$dp[x][i+j][1]+=dp[x][i][1]*(dp[to][j][0]+dp[to][j][1]+dp[to][j][2])$$<\/p>\n<p>$$dp[x][i+j+1][1]+=dp[x][i][0]*dp[to][j][2]$$<\/p>\n<p>\u82e5 $x$ \u6709\u4eba\uff0c $to$ \u6ca1\u6709\u9650\u5236\uff0c\u4f46\u8981\u6ce8\u610f $to$ \u4e0d\u88ab\u5b88\u536b\u65f6\u603b\u7684\u88ab\u5b88\u536b\u7684\u8282\u70b9\u6570\u591a\u4e00\u3002<\/p>\n<p>$$dp[x][i+j][2]+=dp[x][i][2]*(dp[to][j][1]+dp[to][j][2])$$<\/p>\n<p>$$dp[x][i+j+1][2]+=dp[x][i][2]*dp[to][j][0]$$<\/p>\n<p>\u8f6c\u79fb\u65f6\u9700\u8981\u6682\u5b58\u7b54\u6848\u907f\u514d\u8f6c\u79fb\u8fc7\u7a0b\u4e2d\u88ab\u8986\u76d6\u3002<\/p>\n<pre><code class=\"language-cpp\">#include &amp;lt;bits\/stdc++.h&amp;gt;\nusing namespace std;\ntypedef long long ll;\n#define int ll\nconst int maxn=2050,mod=1e9+7,INF=1e9;\nvector&amp;lt;int&amp;gt; g[maxn];\nint dp[maxn][maxn][3],ndp[maxn][3]; \/\/0:\u4e0d\u88ab\u5b88\u536b 1:\u6ca1\u4eba\u4f46\u88ab\u5b88\u536b 2:\u6709\u4eba\nint siz[maxn];\nint ans;\n\nvoid dfs(int x,int fa){\n    dp[x][0][0]=dp[x][1][2]=1;\n    siz[x]=1;\n    for(int to:g[x]){\n        if(to==fa)continue;\n        dfs(to,x);\n        for(int i=0;i&amp;lt;=siz[x];i++){\n            ndp[i][0]=dp[x][i][0];\n            ndp[i][1]=dp[x][i][1];\n            ndp[i][2]=dp[x][i][2];\n            dp[x][i][0]=dp[x][i][1]=dp[x][i][2]=0;\n        }\n        for(int i=siz[x];i&amp;gt;=0;i--){\n            for(int j=siz[to];j&amp;gt;=0;j--){\n                (dp[x][i+j][0]+=ndp[i][0]*(dp[to][j][0]+dp[to][j][1])%mod)%=mod;\n\n                (dp[x][i+j][1]+=ndp[i][1]*(dp[to][j][0]+dp[to][j][1]+dp[to][j][2])%mod)%=mod;\n                (dp[x][i+j+1][1]+=ndp[i][0]*dp[to][j][2]%mod)%=mod;\n\n                (dp[x][i+j][2]+=ndp[i][2]*(dp[to][j][1]+dp[to][j][2])%mod)%=mod;\n                (dp[x][i+j+1][2]+=ndp[i][2]*dp[to][j][0]%mod)%=mod;\n            }\n        }\n        siz[x]+=siz[to];\n    }\n}\n\nvoid solve(){\n    int n;\n    cin&amp;gt;&amp;gt;n;\n\n    for(int i=1;i&amp;lt;n;i++){\n        int x,y;\n        cin&amp;gt;&amp;gt;x&amp;gt;&amp;gt;y;\n        g[x].push_back(y);\n        g[y].push_back(x);\n    }\n\n    ans=INF;\n\n    dfs(1,0);\n    for(int i=0;i&amp;lt;=n;i++){\n        int ans=0;\n        for(int k=0;k&amp;lt;=2;k++){\n            (ans+=dp[1][i][k])%=mod;\n        }\n        cout&amp;lt;&amp;lt;ans&amp;lt;&amp;lt;&amp;#039;\\n&amp;#039;;\n    }\n}\n\nsigned main(){\n    ios::sync_with_stdio(0);\n    int t=1;\n    \/\/ cin&amp;gt;&amp;gt;t;\n    while(t--){\n        solve();\n    }\n\n    return 0;\n}<\/code><\/pre>\n<h3><a href=\"https:\/\/codeforces.com\/problemset\/problem\/815\/C\">Karen and Supermarket<\/a><\/h3>\n<p>\u8bbe $dp[x][i][0\/1]$ \u8868\u793a\u5728\u4ee5 $x$ \u4e3a\u6839\u7684\u5b50\u6811\u5185\uff0c$x$ \u7528\u6216\u8005\u4e0d\u7528\u4f18\u60e0\u5238\u65f6\uff0c\u9009 $i$ \u4ef6\u7269\u54c1\u9700\u8981\u7684\u6700\u5c0f\u4ee3\u4ef7\u3002<\/p>\n<p>\u4e0d\u96be\u53d1\u73b0\uff0c\u5f53\u6240\u5728\u8282\u70b9\u60f3\u8981\u4f7f\u7528\u4f18\u60e0\u5238\u65f6\uff0c\u90a3\u4e48\u5176\u7236\u8282\u70b9\u5fc5\u987b\u4f7f\u7528\u4f18\u60e0\u5238\uff0c\u4e8e\u662f\u53ef\u4ee5\u5f97\u5230\u72b6\u6001\u8f6c\u79fb\u65b9\u7a0b\uff1a<\/p>\n<p>$$dp[x][i+j][0]=min(dp[x][i+j][0],dp[x][i][0]+dp[to][j][0])$$<\/p>\n<p>$$dp[x][i+j][1]=min(dp[x][i+j][1],dp[x][i][1]+dp[to][j][0])$$<\/p>\n<p>$$dp[x][i+j][1]=min(dp[x][i+j][1],dp[x][i][1]+dp[to][j][1])$$<\/p>\n<p>\u6700\u540e\u5224\u65ad\u4e00\u4e0b\u82b1\u8d39\u662f\u5426\u8d85\u8fc7 $b$ \u5143\uff0c\u53d6\u5176\u4e2d\u8d2d\u4e70\u5546\u54c1\u6700\u591a\u7684\u5373\u53ef\u3002<\/p>\n<pre><code class=\"language-cpp\">#include &amp;lt;bits\/stdc++.h&amp;gt;\nusing namespace std;\ntypedef long long ll;\n#define int ll\nconst int maxn=5050,mod=1e9+7,INF=1e18;\nvector&amp;lt;int&amp;gt; g[maxn];\nint c[maxn],d[maxn];\nint dp[maxn][maxn][2]; \/\/ i \u5b50\u6811\u5185\u9009 j \u4ef6\u7269\u54c1\uff0c\u6839\u662f\u5426\u4f7f\u7528\u4f18\u60e0\u7684\u6700\u5c0f\u4ee3\u4ef7\nint siz[maxn];\nint n,k;\n\nvoid dfs(int x,int fa){\n    dp[x][0][0]=0;\n    dp[x][1][0]=c[x];\n    dp[x][1][1]=c[x]-d[x];\n    siz[x]=1;\n    for(int to:g[x]){\n        dfs(to,x);\n        for(int i=siz[x];i&amp;gt;=0;i--){\n            for(int j=siz[to];j&amp;gt;=0;j--){\n                dp[x][i+j][0]=min(dp[x][i+j][0],dp[x][i][0]+dp[to][j][0]);\n                dp[x][i+j][1]=min(dp[x][i+j][1],dp[x][i][1]+dp[to][j][0]);\n                dp[x][i+j][1]=min(dp[x][i+j][1],dp[x][i][1]+dp[to][j][1]);\n            }\n        }\n        siz[x]+=siz[to];\n    }\n}\n\nvoid solve(){\n    cin&amp;gt;&amp;gt;n&amp;gt;&amp;gt;k;\n\n    cin&amp;gt;&amp;gt;c[1]&amp;gt;&amp;gt;d[1];\n\n    for(int i=2;i&amp;lt;=n;i++){\n        int x;\n        cin&amp;gt;&amp;gt;c[i]&amp;gt;&amp;gt;d[i]&amp;gt;&amp;gt;x;\n        g[x].push_back(i);\n    }\n\n    for(int i=0;i&amp;lt;=n;i++){\n        for(int j=0;j&amp;lt;=n;j++){\n            dp[i][j][0]=dp[i][j][1]=INF;\n        }\n    }\n\n    dfs(1,0);\n\n    int ans=0;\n    for(int i=n;i&amp;gt;=0;i--){\n        if(min(dp[1][i][0],dp[1][i][1])&amp;lt;=k){\n            ans=i;\n            break;\n        }\n    }\n    cout&amp;lt;&amp;lt;ans&amp;lt;&amp;lt;&amp;#039;\\n&amp;#039;;\n}\n\nsigned main(){\n    ios::sync_with_stdio(0);\n    int t=1;\n    \/\/ cin&amp;gt;&amp;gt;t;\n    while(t--){\n        solve();\n    }\n\n    return 0;\n}<\/code><\/pre>\n<h3><a href=\"https:\/\/atcoder.jp\/contests\/abc416\/tasks\/abc416_f\">Paint Tree 2<\/a><\/h3>\n<p>\u8981\u6c42\u6d82\u6811\u4e0a\u6700\u591a $k$ \u6761\u4e92\u4e0d\u76f8\u4ea4\u94fe\uff0c\u6700\u5927\u5316\u94fe\u4e0a\u8282\u70b9\u7684\u6743\u503c\u548c\u3002\u53ef\u4ee5\u53d1\u73b0\u8282\u70b9\u8981\u4e48\u4e0d\u5728\u94fe\u4e0a\uff0c\u8981\u4e48\u5728\u94fe\u7684\u7aef\u70b9\uff0c\u8981\u4e48\u5728\u94fe\u7684\u4e2d\u95f4\uff0c\u4e8e\u662f\u53ef\u4ee5\u8bbe $dp[x][i][0\/1\/2]$\uff0c\u8868\u793a\u5728\u4ee5 $x$ \u4e3a\u6839\u7684\u5b50\u6811\u5185\uff0c$x$ \u4e0d\u5728\u94fe\u4e0a\u6216\u5728\u94fe\u7684\u7aef\u70b9\u6216\u5728\u94fe\u7684\u4e2d\u95f4\uff0c\u9009 $i$ \u94fe\u7684\u6700\u5927\u4ef7\u503c\u548c\u3002<\/p>\n<p>\u4ee4 $mx=max{dp[to][j][0],dp[to][j][1],dp[to][j][2]}$\u3002<\/p>\n<p>\u82e5 $x$ \u4e0d\u5728\u94fe\u4e0a\uff0c\u90a3\u4e48 $to$ \u6ca1\u6709\u9650\u5236\uff0c\u53d6\u6700\u5927\u4ef7\u503c\u5373\u53ef\u3002<\/p>\n<p>$$dp[x][i+j][0]=max(dp[x][i+j][0],dp[x][i][0]+mx)$$<\/p>\n<p>\u82e5 $x$ \u5728\u94fe\u7684\u7aef\u70b9\uff0c\u6b64\u65f6\u6709\u4e24\u79cd\u60c5\u51b5\uff1a\u7b2c\u4e00\u79cd\u662f $x$ \u539f\u6765\u5c31\u5728\u94fe\u7684\u7aef\u70b9\uff0c $to$ \u6ca1\u6709\u9650\u5236\uff1b\u7b2c\u4e8c\u79cd\u662f $x$ \u539f\u6765\u4e0d\u5728\u94fe\u4e0a\uff0c $to$ \u5728\u94fe\u7684\u7aef\u70b9\uff0c\u6b64\u65f6\u4e24\u8005\u53ef\u4ee5\u76f8\u8fde\u3002<\/p>\n<p>$$dp[x][i+j][1]=max(dp[x][i+j][1],dp[x][i][1]+mx)$$<br \/>\n$$dp[x][i+j][1]=max(dp[x][i+j][1],dp[x][i][0]+dp[to][j][1]+a[x])$$<\/p>\n<p>\u82e5 $x$ \u5728\u94fe\u7684\u4e2d\u95f4\uff0c\u6b64\u65f6\u6709\u4e24\u79cd\u60c5\u51b5\uff1a\u7b2c\u4e00\u79cd\u662f $x$ \u539f\u6765\u5c31\u5728\u94fe\u7684\u4e2d\u95f4\uff0c $to$ \u6ca1\u6709\u9650\u5236\uff1b\u7b2c\u4e8c\u79cd\u662f $x$ \u539f\u6765\u5728\u94fe\u7684\u7aef\u70b9\uff0c $to$ \u4e5f\u5728\u94fe\u7684\u7aef\u70b9\uff0c\u6b64\u65f6\u4e24\u8005\u53ef\u4ee5\u76f8\u8fde\uff0c\u94fe\u6570\u51cf\u4e00\u3002<\/p>\n<p>$$dp[x][i+j][2]=max(dp[x][i+j][2],dp[x][i][2]+mx)$$<br \/>\n$$dp[x][i+j-1][2]=max(dp[x][i+j-1][2],dp[x][i][1]+dp[to][j][1])$$<\/p>\n<p>\u8f6c\u79fb\u65f6\u9700\u8981\u6682\u5b58\u7b54\u6848\u907f\u514d\u8f6c\u79fb\u8fc7\u7a0b\u4e2d\u88ab\u8986\u76d6\u3002<\/p>\n<pre><code class=\"language-cpp\">#include &amp;lt;bits\/stdc++.h&amp;gt;\nusing namespace std;\ntypedef long long ll;\n#define int ll\nconst int maxn=200050,mod=1e9+7,INF=1e18;\nvector&amp;lt;int&amp;gt; g[maxn];\nint a[maxn];\nint dp[maxn][10][3],ndp[10][3]; \/\/0:\u6ca1\u9009  1:\u94fe\u7684\u7aef\u70b9  2:\u94fe\u7684\u4e2d\u95f4\nint n,k;\n\nvoid dfs(int x,int fa){\n    dp[x][0][0]=0;\n    dp[x][1][1]=dp[x][1][2]=a[x];\n    for(int to:g[x]){\n        if(to==fa)continue;\n        dfs(to,x);\n        for(int i=0;i&amp;lt;=k;i++){\n            ndp[i][0]=ndp[i][1]=ndp[i][2]=-INF;\n        }\n        for(int i=0;i&amp;lt;=k;i++){\n            for(int j=0;j&amp;lt;=k;j++){\n                if(i+j-1&amp;gt;k)continue;\n                int mx=max(dp[to][j][0],max(dp[to][j][1],dp[to][j][2]));\n                ndp[i+j][0]=max(ndp[i+j][0],dp[x][i][0]+mx);\n\n                ndp[i+j][1]=max(ndp[i+j][1],dp[x][i][1]+mx);\n                ndp[i+j][1]=max(ndp[i+j][1],dp[x][i][0]+dp[to][j][1]+a[x]);\n\n                ndp[i+j][2]=max(ndp[i+j][2],dp[x][i][2]+mx);\n                if(i+j&amp;gt;=1)ndp[i+j-1][2]=max(ndp[i+j-1][2],dp[x][i][1]+dp[to][j][1]);\n            }\n        }\n        for(int i=0;i&amp;lt;=k;i++){\n            dp[x][i][0]=ndp[i][0];\n            dp[x][i][1]=ndp[i][1];\n            dp[x][i][2]=ndp[i][2];\n        }\n    }\n}\n\nvoid solve(){\n    cin&amp;gt;&amp;gt;n&amp;gt;&amp;gt;k;\n\n    for(int i=1;i&amp;lt;=n;i++){\n        cin&amp;gt;&amp;gt;a[i];\n    }\n\n    for(int i=1;i&amp;lt;n;i++){\n        int x,y;\n        cin&amp;gt;&amp;gt;x&amp;gt;&amp;gt;y;\n        g[x].push_back(y);\n        g[y].push_back(x);\n    }\n\n    for(int i=1;i&amp;lt;=n;i++){\n        for(int j=0;j&amp;lt;=k;j++){\n            dp[i][j][0]=dp[i][j][1]=dp[i][j][2]=-INF;\n        }\n    }\n    dfs(1,0);\n\n    int ans=0;\n    for(int i=0;i&amp;lt;=k;i++){\n        ans=max(ans,max(dp[1][i][0],max(dp[1][i][1],dp[1][i][2])));\n    }\n    cout&amp;lt;&amp;lt;ans&amp;lt;&amp;lt;&amp;#039;\\n&amp;#039;;\n}\n\nsigned main(){\n    ios::sync_with_stdio(0);\n    int t=1;\n    \/\/ cin&amp;gt;&amp;gt;t;\n    while(t--){\n        solve();\n    }\n\n    return 0;\n}<\/code><\/pre>\n<h3><a href=\"https:\/\/www.luogu.com.cn\/problem\/P4516\">\u6f5c\u5165\u884c\u52a8<\/a><\/h3>\n<p>\u8bbe $dp[x][i][0\/1][0\/1]$ \u8868\u793a\u5728\u4ee5 $x$ \u4e3a\u6839\u7684\u5b50\u6811\u5185\uff0c\u653e\u4e86 $i$ \u4e2a\u76d1\u542c\u8bbe\u5907\uff0c$x$ \u8282\u70b9\u6709\u65e0\u8bbe\u5907\uff0c$x$ \u8282\u70b9\u662f\u5426\u88ab\u76d1\u542c\u7684\u65b9\u6848\u6570\u3002\u9700\u8981\u8ba8\u8bba\u4ee5\u4e0b\u56db\u79cd\u60c5\u51b5\u3002<\/p>\n<p>\u82e5 $x$ \u6ca1\u653e\u8bbe\u5907\u4e14\u6ca1\u88ab\u76d1\u542c\uff0c\u90a3\u4e48 $to$ \u4e00\u5b9a\u4e0d\u80fd\u653e\u8bbe\u5907\u5e76\u4e14\u4e00\u5b9a\u88ab\u76d1\u542c\u3002<\/p>\n<p>$$dp[x][i+j][0][0]+=dp[x][i][0][0]*dp[to][j][0][1]$$<\/p>\n<p>\u82e5 $x$ \u653e\u4e86\u8bbe\u5907\u4f46\u6ca1\u88ab\u76d1\u542c\uff0c\u90a3\u4e48 $to$ \u4e00\u5b9a\u4e0d\u80fd\u653e\u8bbe\u5907\uff0c\u662f\u5426\u88ab\u76d1\u542c\u65e0\u6240\u8c13\u3002<\/p>\n<p>$$dp[x][i+j][1][0]+=dp[x][i][1][0]*(dp[to][j][0][0]+dp[to][j][0][1])$$<\/p>\n<p>\u82e5 $x$ \u6ca1\u653e\u8bbe\u5907\u4f46\u88ab\u76d1\u542c\uff0c\u6b64\u65f6\u6709\u4e24\u79cd\u60c5\u51b5\uff1a\u7b2c\u4e00\u79cd\u662f $x$ \u539f\u6765\u5c31\u6ca1\u653e\u8bbe\u5907\u4f46\u88ab\u76d1\u542c\uff0c\u90a3\u4e48\u53ea\u9700 $to$ \u88ab\u76d1\u542c\uff1b\u7b2c\u4e8c\u79cd\u662f $x$ \u539f\u6765\u6ca1\u653e\u8bbe\u5907\u4e14\u6ca1\u88ab\u76d1\u542c\uff0c\u90a3\u4e48 $to$ \u4e00\u5b9a\u8981\u653e\u4e86\u8bbe\u5907\u4e14\u88ab\u76d1\u542c\u3002<\/p>\n<p>$$dp[x][i+j][0][1]+=dp[x][i][0][1]<em>(dp[to][j][0][1]+dp[to][j][1][1])$$<br \/>\n$$dp[x][i+j][0][1]+=dp[x][i][0][0]<\/em>dp[to][j][1][1]$$<\/p>\n<p>\u82e5 $x$ \u653e\u4e86\u8bbe\u5907\u4e14\u88ab\u76d1\u542c\uff0c\u6b64\u65f6\u6709\u4e24\u79cd\u60c5\u51b5\uff1a\u7b2c\u4e00\u79cd\u662f $x$ \u539f\u6765\u5c31\u653e\u4e86\u8bbe\u5907\u4e14\u88ab\u76d1\u542c\uff0c\u90a3\u4e48 $to$ \u6ca1\u6709\u9650\u5236\uff1b\u7b2c\u4e8c\u79cd\u662f $x$ \u539f\u6765\u653e\u4e86\u8bbe\u5907\u4f46\u6ca1\u88ab\u76d1\u542c\uff0c\u90a3\u4e48 $to$ \u653e\u4e86\u8bbe\u5907\u5c31\u884c\u3002<\/p>\n<p>$$dp[x][i+j][1][1]+=dp[x][i][1][1]*(dp[to][j][0][0]+dp[to][j][1][0]+dp[to][j][0][1]+dp[to][j][1][1])$$<\/p>\n<p>$$dp[x][i+j][1][1]+=dp[x][i][1][0]*(dp[to][j][1][0]+dp[to][j][1][1])$$<\/p>\n<p>\u8f6c\u79fb\u65f6\u9700\u8981\u6682\u5b58\u7b54\u6848\u907f\u514d\u8f6c\u79fb\u8fc7\u7a0b\u4e2d\u88ab\u8986\u76d6\u3002dp \u6570\u7ec4\u5f00 long long \u4f1a MLE\uff0c\u6240\u4ee5\u53ea\u80fd\u5728\u8fd0\u7b97\u8fc7\u7a0b\u4e2d\u8f6c\u4e3a long long \u8ba1\u7b97\u3002<\/p>\n<pre><code class=\"language-cpp\">#include &amp;lt;bits\/stdc++.h&amp;gt;\nusing namespace std;\ntypedef long long ll;\nconst int maxn = 100050, mod = 1e9 + 7, INF = 1e9;\nvector&amp;lt;int&amp;gt; g[maxn];\nint dp[maxn][105][2][2], ndp[105][2][2]; \/\/\u6709\u65e0\u8bbe\u5907\uff0c\u662f\u5426\u88ab\u76d1\u542c\nint siz[maxn];\nint n, k;\n\nvoid dfs(int x, int fa) {\n    dp[x][0][0][0] = dp[x][1][1][0] = 1;\n    siz[x] = 1;\n    for (int to : g[x]) {\n        if (to == fa)continue;\n        dfs(to, x);\n        for (int i = 0;i &amp;lt;= min(k, siz[x]);i++) {\n            ndp[i][0][0] = dp[x][i][0][0];\n            ndp[i][1][0] = dp[x][i][1][0];\n            ndp[i][0][1] = dp[x][i][0][1];\n            ndp[i][1][1] = dp[x][i][1][1];\n            dp[x][i][0][0] = dp[x][i][1][0] = dp[x][i][0][1] = dp[x][i][1][1] = 0;\n        }\n\n        for (int i = 0;i &amp;lt;= min(k, siz[x]);i++) {\n            for (int j = 0;j &amp;lt;= min(k, siz[to]);j++) {\n                if(i+j&amp;gt;k)continue;\n                (dp[x][i+j][0][0]=1ll*dp[x][i+j][0][0]+1ll*ndp[i][0][0]*dp[to][j][0][1]%mod) %= mod;\n\n                (dp[x][i+j][1][0]=1ll*dp[x][i+j][1][0]+1ll*ndp[i][1][0]*(1ll*dp[to][j][0][0]+dp[to][j][0][1])%mod) %= mod;\n\n                (dp[x][i+j][0][1]=1ll*dp[x][i+j][0][1]+1ll*ndp[i][0][1]*(1ll*dp[to][j][0][1]+dp[to][j][1][1])%mod) %= mod;\n                (dp[x][i+j][0][1]=1ll*dp[x][i+j][0][1]+1ll*ndp[i][0][0]*dp[to][j][1][1]%mod) %= mod;\n\n                (dp[x][i+j][1][1]=1ll*dp[x][i+j][1][1]+1ll*ndp[i][1][1]*(1ll*dp[to][j][0][0]+dp[to][j][1][0]+dp[to][j][0][1]+dp[to][j][1][1])%mod) %= mod;\n                (dp[x][i+j][1][1]=1ll*dp[x][i+j][1][1]+1ll*ndp[i][1][0]*(1ll*dp[to][j][1][0]+dp[to][j][1][1])%mod) %= mod;\n            }\n        }\n        siz[x] += siz[to];\n    }\n}\n\nvoid solve() {\n    cin &amp;gt;&amp;gt; n &amp;gt;&amp;gt; k;\n\n    for (int i = 1;i &amp;lt; n;i++) {\n        int x, y;\n        cin &amp;gt;&amp;gt; x &amp;gt;&amp;gt; y;\n        g[x].push_back(y);\n        g[y].push_back(x);\n    }\n\n    dfs(1, 0);\n\n    cout &amp;lt;&amp;lt; (1ll*dp[1][k][0][1]+dp[1][k][1][1])%mod &amp;lt;&amp;lt; &amp;#039;\\n&amp;#039;;\n}\n\nsigned main() {\n    ios::sync_with_stdio(0);\n    int t = 1;\n    \/\/ cin&amp;gt;&amp;gt;t;\n    while (t--) {\n        solve();\n    }\n\n    return 0;\n}<\/code><\/pre>\n<h2>\u603b\u7ed3<\/h2>\n<ul>\n<li>\u4e3b\u8981\u601d\u8def\u662f\u4ece\u5b50\u8282\u70b9\u5411\u7236\u8282\u70b9\u8f6c\u79fb\uff0c\u8ba8\u8bba\u53ef\u80fd\u51fa\u73b0\u7684\u60c5\u51b5\uff0c\u679a\u4e3e\u5b50\u6811\u4e2d\u7269\u54c1\u7684\u5206\u914d\uff0c\u83b7\u5f97\u5f53\u524d\u5b50\u6811\u7684\u4ef7\u503c<\/li>\n<li>\u6ce8\u610f dp \u6570\u7ec4\u7684\u521d\u59cb\u5316\u662f\u5bf9\u5f53\u524d\u5b50\u6811\u8003\u8651<\/li>\n<li>\u6ce8\u610f\u63a7\u5236\u597d\u679a\u4e3e\u7684\u65b9\u5411\u548c\u4e0a\u4e0b\u754c<\/li>\n<li>\u6ce8\u610f\u8f6c\u79fb\u65f6\u662f\u5426\u4f1a\u88ab\u8986\u76d6<\/li>\n<\/ul>\n","protected":false},"excerpt":{"rendered":"<p>\u8fd9\u7c7b\u9898\u611f\u89c9\u76f8\u5bf9\u662f\u6bd4\u8f83\u5957\u8def\u7684\uff0c\u4f46\u5b9e\u9645\u5199\u8d77\u6765\u5751\u70b9\u6bd4\u8f83\u591a\uff0c\u5982\u9700\u8981\u63a7\u5236\u597d\u679a\u4e3e\u7684\u4e0a\u4e0b\u754c\uff0c\u4ee5\u53ca\u8981\u8003\u8651\u65b0\u72b6\u6001\u662f\u5426\u4f1a\u88ab\u8986\u76d6\u7b49\u95ee [&hellip;]<\/p>\n","protected":false},"author":2,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[2,3,10],"tags":[],"class_list":["post-546","post","type-post","status-publish","format-standard","hentry","category-c","category-oi","category-10"],"_links":{"self":[{"href":"https:\/\/www.xgnd.net\/index.php\/wp-json\/wp\/v2\/posts\/546","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.xgnd.net\/index.php\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.xgnd.net\/index.php\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.xgnd.net\/index.php\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.xgnd.net\/index.php\/wp-json\/wp\/v2\/comments?post=546"}],"version-history":[{"count":3,"href":"https:\/\/www.xgnd.net\/index.php\/wp-json\/wp\/v2\/posts\/546\/revisions"}],"predecessor-version":[{"id":548,"href":"https:\/\/www.xgnd.net\/index.php\/wp-json\/wp\/v2\/posts\/546\/revisions\/548"}],"wp:attachment":[{"href":"https:\/\/www.xgnd.net\/index.php\/wp-json\/wp\/v2\/media?parent=546"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.xgnd.net\/index.php\/wp-json\/wp\/v2\/categories?post=546"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.xgnd.net\/index.php\/wp-json\/wp\/v2\/tags?post=546"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}