mirror of
https://github.com/Kiritow/OJ-Problems-Source.git
synced 2024-03-22 13:11:29 +08:00
54 lines
1.0 KiB
C++
54 lines
1.0 KiB
C++
#include<iostream>
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#include<cstdio>
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#include<cstring>
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#include<algorithm>
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using namespace std;
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#define MAXN 100100
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#pragma comment(linker, "/STACK:16777216")
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struct Edge{
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int v,next;
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}edge[MAXN*4];
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int NE;
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long long n;
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int head[MAXN];
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void Insert(int u,int v)
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{
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edge[NE].v=v;
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edge[NE].next=head[u];
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head[u]=NE++;
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}
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bool mark[MAXN];
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long long sum,ans;
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int dfs(int u)
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{
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mark[u]=true;
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int son,tmp=0;
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for(int i=head[u];i!=-1;i=edge[i].next){
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int v=edge[i].v;
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if(mark[v])continue;
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son=dfs(v);
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tmp+=son;
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ans+=(long long )(n-1-tmp)*son;
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}
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return tmp+1;
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}
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int main()
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{
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int u,v;
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while(~scanf("%I64d",&n)){
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NE=0;
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memset(head,-1,sizeof(head));
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for(int i=1;i<n;i++){
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scanf("%d%d",&u,&v);
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Insert(u,v);
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Insert(v,u);
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}
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memset(mark,false,sizeof(mark));
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ans=0;
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dfs(1);
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sum=n*(n-1)*(n-2)/6;
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printf("%I64d\n",sum-ans);
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}
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return 0;
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}
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