POJ -- 3140

 1     #include<iostream>
 2     #include<cstdio>
 3     #include<cstring>
 4     #include<string>
 5     #define MAXN 1000010
 6     #define LL long long
 7     const LL INF = 0x7fffffffffffff;
 8     using namespace std;
 9     typedef struct{
10         int to,next;
11     }Node;
12     Node edge[2*MAXN];
13     int vis[MAXN/10],head[MAXN/10],val[MAXN/10];
14     LL sum[MAXN/10],all_sum,ans;
15     LL My_abs(LL tmp){return tmp < 0 ? -tmp : tmp;}
16     void addedge(int u,int v,int k){
17         edge[k].to = v;
18         edge[k].next = head[u];
19         head[u] = k;
20     }
21     LL dfs_sum(int s){
22         vis[s] = 1;
23         sum[s] = val[s];
24         for(int i = head[s];~i;i = edge[i].next){
25             int u = edge[i].to;
26             if(!vis[u]) sum[s] += dfs_sum(u);
27         }
28         return sum[s];
29     }
30     void dfs_minabs(int s){
31         vis[s]= 1;
32         for(int i  = head[s];~i;i = edge[i].next){
33             int u = edge[i].to;
34             if(!vis[u]){
35                 dfs_minabs(u);
36                 ans = min(ans,My_abs(all_sum - 2*sum[u]));
37             }
38         }
39     }
40     int main(){
41         int n,m,cas = 0;
42         freopen("in.c","r",stdin);
43         while(~scanf("%d%d",&n,&m) && (m+n) ){
44             int k = 1,tmp,u,v;
45             all_sum = 0;
46             for(int i = 1;i <= n;i ++) scanf("%d",&tmp),val[i] = tmp,all_sum += tmp;
47             memset(head,-1,sizeof(head));
48             for(int i = 0;i < m;i ++){
49                 scanf("%d%d",&u,&v);
50                 addedge(u,v,k++);
51                 addedge(v,u,k++);
52             }
53             memset(vis,0,sizeof(vis));
54             dfs_sum(1);
55             ans = INF;
56             memset(vis,0,sizeof(vis));
57             dfs_minabs(1);
58             if(n == 1) ans = val[1];
59             printf("Case %d: %lld\n",++cas,ans);
60         }
61         return 0;
62     }