HDU 4705 Y （2013多校10,1010题，简单树形DP）

Y

Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 131072/131072 K (Java/Others)
Total Submission(s): 60    Accepted Submission(s): 20

Problem Description

Sample Input

4
1 2
1 3
1 4

Sample Output

1

Hint

1. The only set is {2,3,4}.

2. Please use #pragma comment(linker, "/STACK:16777216")

Source

2013 Multi-University Training Contest 10

Recommend

zhuyuanchen520

树形DP统计一遍就可以了。

 /* ***********************************************
 Author        :kuangbin
 Created Time  :2013/8/22 12:27:59
 File Name     :F:\2013ACM练习\2013多校10\1010.cpp
 ************************************************ */
 #pragma comment(linker, "/STACK:1024000000,1024000000")
 #include <stdio.h>
 #include <string.h>
 #include <iostream>
 #include <algorithm>
 #include <vector>
 #include <queue>
 #include <set>
 #include <map>
 #include <string>
 #include <math.h>
 #include <stdlib.h>
 #include <time.h>
 using namespace std;

 const int MAXN = ;
 struct Edge
 {
     int to,next;
 }edge[MAXN*];
 int head[MAXN],tot;
 void init()
 {
     memset(head,-,sizeof(head));
     tot = ;
 }
 void addedge(int u,int v)
 {
     edge[tot].to = v;
     edge[tot].next = head[u];
     head[u] = tot++;
 }

 int num[MAXN];
 int n;
 long long ans;
 void dfs(int u,int pre)
 {
     num[u] = ;
     int tmp = ;
     for(int i = head[u];i!= -;i = edge[i].next)
     {
         int v = edge[i].to;
         if(v == pre)continue;
         dfs(v,u);
         ans += (long long)tmp*num[v];
         num[u] += num[v];
         tmp += num[v];
     }
     ans += (long long)tmp*(n-num[u]);
 }

 int main()
 {
     //freopen("in.txt","r",stdin);
     //freopen("out.txt","w",stdout);
     int u,v;
     while(scanf("%d",&n) == )
     {
         init();
         for(int i = ;i < n;i++)
         {
             scanf("%d%d",&u,&v);
             addedge(u,v);
             addedge(v,u);
         }
         ans = ;
         dfs(,-);
         long long tot = (long long)n*(n-)*(n-)/;
         printf("%I64d\n",tot-ans);
     }
     return ;
 }