POJ 3140 Contestants Division (水题)

#include<cstdio>
#include<cstring>
#include<algorithm>
#include<iostream>

#define abs(x)  ((x) >= 0 ? (x) : -(x))
using namespace std;
typedef __int64 LL;
const LL maxn = 100005;
const LL INF = 0x3f3f3f3f3f3f3f3f;

struct Nod{
LL b,next;
void init(LL b,LL next){
this->b=b;this->next=next;
}
}buf[maxn<<1];
LL len,E[maxn];

LL n,m,sum,vi[maxn],num[maxn],dp[maxn];

void init(){
len=0;sum=0;
memset(E,-1,sizeof(E));
memset(dp,0,sizeof(dp));
}

void add_edge(LL a,LL b){
buf[len].init(b,E[a]);E[a]=len++;
buf[len].init(a,E[b]);E[b]=len++;
}

void dfs(LL u,LL pre){
LL i,v;
num[u] = vi[u];
for(i=E[u];i!=-1;i=buf[i].next){
v=buf[i].b;
if(v == pre) continue;
dfs(v,u);
num[u] += num[v];
}
dp[u] = abs(sum - 2*num[u]);
}

int main(){
LL i,j,a,b,o,cas=0;
while(scanf("%I64d%I64d",&n,&m),n+m){
init();
for(i=1;i<=n;i++){
scanf("%I64d",&vi[i]);
sum += vi[i];
}
while(m--){
scanf("%I64d%I64d",&a,&b);
add_edge(a,b);
}
dfs(1,-1);
o = INF;
//cout<<sum<<endl;
//for(int i=1;i<=n;i++) cout<<num[i]<<" "; cout<<endl;
//for(int i=1;i<=n;i++) cout<<dp[i]<<" "; cout<<endl;
for(int i=1;i<=n;i++) o = min(o,dp[i]);
printf("Case %I64d: %I64d\n",++cas,o);
}
return 0;
}