POJ--3140--Contestants Division

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题目大意：求一棵树被划分成两部分之后，这两部分权值和的差的绝对值的最小值

水题无误了，因为long long 没处理好WA了几次，略坑爹

#include<iostream>#include<cstring>#include<cstdio>#include<vector>#define maxn 100005using namespace std;typedef long long LL;template <typename T>T oabs(T a){return a<0?-a:a;}template<typename T>T omin(T a,T b){return a<b?a:b;}LL tot,ans;int ka;int p[maxn];LL num[maxn];vector<int> g[maxn];int n,m;bool init(){int x,y;scanf("%d%d",&n,&m);if(n+m==0)return false;tot=0;for(int i=1;i<=n;i++){scanf("%lld",&num[i]);tot+=num[i];g[i].clear();}for(int i=0;i<m;i++){scanf("%d%d",&x,&y);g[x].push_back(y);g[y].push_back(x);}ans=tot+1;return true;}void build(int u){for(int i=0;i<g[u].size();i++){int v=g[u][i];if(v==p[u])continue;p[v]=u;build(v);}}void dfs(int u){LL temp;for(int i=0;i<g[u].size();i++){int v=g[u][i];if(v==p[u])continue;dfs(v);num[u]+=num[v];}temp=oabs(tot-num[u]-num[u]);ans=omin(ans,temp);}void solve(){memset(p,-1,sizeof(p));build(1);dfs(1);printf("Case %d: ",ka++);printf("%lld\n",ans);}int main(){ka=1;while(init())solve();return 0;}