poj3140Contestants Division

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这叫树形DP吗。。？断开某条边 求剩下两颗树数权值和的差最小

dfs一遍 枚举边 查了n久 wa n次  dp数组没初始化。。

在poj上1A感觉应该挺爽

 #include <iostream>
 #include<cstdio>
 #include<cstring>
 #include<algorithm>
 #include<stdlib.h>
 using namespace std;
 #define N 100010
 #define M 1000010
 #define LL long long
 LL dp[M<<],p[N];
 struct node
 {
     int u,v,next;
 }ed[M<<];
 int head[N],t,n,m;
 void init()
 {
     t = ;
     memset(head,-,sizeof(head));
 }
 void add(int u,int v)
 {
     ed[t].u = u;
     ed[t].v = v;
     ed[t].next = head[u];
     head[u] = t++;
 }
 LL dfs(int pre,int u,int e)
 {
     int i;
     LL sum=p[u];
     for(i = head[u] ; i != - ; i = ed[i].next)
     {
         int v = ed[i].v;
         if(v==pre)
         continue;
         sum+=dfs(u,v,i);
     }
     dp[e] = sum;
     return dp[e];
 }
 int main()
 {
     int i,kk=;
     while(scanf("%d%d",&n,&m)!=EOF)
     {
         if(n==&&m==)
         break;
         init();kk++;
         memset(dp,,sizeof(dp));
         LL s=;
         for(i =; i <= n; i++)
         {
             scanf("%lld",&p[i]);
             s+=p[i];
         }
         for(i = ; i <= m ;i++)
         {
             int u,v;
             scanf("%d%d",&u,&v);
             add(u,v);
             add(v,u);
         }
         dfs(-,i,);
         LL ans = s,o;
         for(i =  ; i < t ; i++)
         {
             if(s-dp[i]>dp[i])
             o = s-dp[i]-dp[i];
             else
             o = dp[i]-(s-dp[i]);
             if(o<ans)
             ans = o;
         }
         printf("Case %d: ",kk);
         printf("%lld\n",ans);
     }
     return ;
 }