mirror of
https://github.com/Kiritow/OJ-Problems-Source.git
synced 2024-03-22 13:11:29 +08:00
52 lines
1.2 KiB
C++
52 lines
1.2 KiB
C++
#include <bitset>
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#include <iostream>
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using namespace std;
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const int maxn=2013;
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int first[maxn],pre[maxn],vv[maxn*20],nxt[maxn*20];
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bitset<2001> to[2001];
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bool vis[maxn];
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int ans;
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void dfs(int u,int p)
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{
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vis[u]=true;
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to[u].reset();
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for(int e=pre[u];e;e=nxt[e]) if(vis[vv[e]])
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to[u].set(vv[e]);
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for(int e=first[u];e;e=nxt[e]) if(vv[e]!=p)
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dfs(vv[e],u);
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if(p==-1)
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return;
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if(to[u].test(p))
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ans++;
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else
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to[p]|=to[u];
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}
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int main()
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{
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int n,m;
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while(~scanf("%d%d",&n,&m) && n|m)
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{
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memset(vis,0,sizeof(vis));
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memset(first,0,sizeof(first));
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memset(pre,0,sizeof(pre));
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int e=2;
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for(int i=1;i<n;i++)
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{
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int u,v;
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scanf("%d%d",&u,&v);
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nxt[e]=first[u],vv[e]=v,first[u]=e++;
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nxt[e]=first[v],vv[e]=u,first[v]=e++;
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}
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for(int i=n;i<=m;i++)
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{
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int u,v;
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scanf("%d%d",&u,&v);
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nxt[e]=pre[u],vv[e]=v,pre[u]=e++;
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nxt[e]=pre[v],vv[e]=u,pre[v]=e++;
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}
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ans=0;
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dfs(1,-1);
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printf("%d\n",ans);
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}
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}
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