hdu 3047 Zjnu Stadium 带权并查集

#include<cstdio>
#include<cmath>
using namespace std;

const int maxn = 50005;
int f[maxn], rank[maxn];
int n, m;

void init(){
    for (int i = 0; i <= n; ++i){
        f[i] = i;
        rank[i] = 0;
    }
    return;
}

int find(int x){
    if (x == f[x])
        return f[x];
    int t = f[x];
    f[x] = find(f[x]);
    rank[x] += rank[t];        //把父辈的加起来
    return f[x];
}

bool Union(int x, int y, int m){
    int a = find(x);
    int b = find(y);
    if (a == b){
        if (rank[x] + m != rank[y])
            return false;
        return true;
    }
    f[b] = a;
    rank[b] = rank[x] + m - rank[y];
    return true;
}

int main(){
    int a, b, x;
    while (~scanf("%d%d", &n, &m)){
        init();
        int cnt = 0;
        for (int i = 0; i<m; ++i){
            scanf("%d%d%d", &a, &b, &x);
            if (!Union(a, b, x)){
                cnt++;
            }
        }
        printf("%d\n", cnt);
    }
    return 0;
}