HDU 2242 考研路茫茫——空调教室

考研路茫茫——空调教室

http://acm.hdu.edu.cn/showproblem.php?pid=2242

分析：

　　树形dp，删边。

代码：

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

 using namespace std;

 const int MAXN = ;
 const int MAXM = ;

 struct Edge{
     int to,nxt;
 }e[MAXM];
 int head[MAXM],tot;
 int son[MAXN],Sum,ans;

 inline int read() {
     int x = ,f = ;char ch = getchar();
     for (; ch<''||ch>''; ch = getchar())
         if (ch=='-') f = -;
     for (; ch>=''&&ch<=''; ch = getchar())
         x = x*+ch-'';
     return x*f;
 }
 inline void add_edge(int u,int v) {
     e[++tot].to = v,e[tot].nxt = head[u],head[u] = tot;
 }
 inline void init() {
     memset(head,,sizeof(head));
     ans = 1e9; // ans也要初始化！！！
     tot = Sum = ;
 }
 void dfs(int u,int fa) {
     for (int i=head[u]; i; i=e[i].nxt) {
         int v = e[i].to;
         if (v==fa) continue;
         dfs(v,u);
         son[u] += son[v];
         ans = min(ans,abs(Sum-son[v]-son[v]));
     }
 }

 int main() {
     int n,m,CASE = ;
     while (scanf("%d%d",&n,&m)!=EOF) {
         init();
         for (int i=; i<=n; ++i) son[i] = read(),Sum += son[i];
         for (int u,v,i=; i<=m; ++i) {
             u = read(),v = read();
             add_edge(u,v),add_edge(v,u);
         }
         dfs(,-);
         printf("Case %d: %d\n",++CASE,ans);
     }
     return ;
 }