POJ - 3140 Contestants Division DFS計數+假樹形DP

坑點，long long 不能用abs

AC代碼：

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

using namespace std;
typedef long long ll;
const int maxn = 1000100;
const ll inf = 0x3f3f3f3f3f3f3f3f;
struct node {
    ll u, v, w, next;
}edge[maxn * 2];
int tot;
int head[maxn];
void addedge(int u, int v, int w) {
    edge[tot].u = u;
    edge[tot].v = v;
    edge[tot].w = w;
    edge[tot].next = head[u];
    head[u] = tot ++;
}
ll num[100100];
void DFS(int u, int fa) {
    for (int i = head[u]; i != -1; i = edge[i].next) {
        int v = edge[i].v;
        if(v == fa) continue;
        DFS(v, u);
        num[u] += num[v];
    }
}
ll solve(ll x) {
    return x > 0 ? x : -x;
}
int main() {
    int n, m;
    int kase = 0;
    while(~scanf("%d%d", &n, &m) && (n + m)) {
        tot = 0;
        memset(head, -1, sizeof(head));
        memset(num, 0, sizeof(num));
        long long sum = 0;
        for (int i = 1; i <= n; i++) {
            scanf("%lld", &num[i]);
            sum += num[i];
        }
        for (int i = 1; i <= m; i++) {
            int u, v;
            scanf("%d%d", &u, &v);
            addedge(u, v, 1);
            addedge(v, u, 1);
        }
        DFS(1, 1);
        ll min_ = inf;
        for (int i = 1; i <= n; i++) {
            ll cnt = num[i];
            ll cns = sum - num[i];
            min_ = min(min_, solve(cnt - cns));
        }
        printf("Case %d: %lld\n", ++kase, min_);
    }
}