hdu 3038 并查集

题目：给出一些询问，[l,r]的和为s，问有多少个是错的

//并查集 ，，sum[a]表示a与父亲这条路径上的和
#include <iostream>
#include <cstdio>
#include <cstring>
#include <algorithm>

using namespace std;

const int maxn = 2e5 + 5;
int fa[maxn], sum[maxn];
int n, m, l, r, s;
int findFa(int x){
    if (x != fa[x]){
        int t = fa[x];
        fa[x] = findFa(fa[x]);
        sum[x] += sum[t];
    }
    return fa[x];
}
int main(){
    while (~scanf("%d%d", &n, &m)){
        for (int i = 0; i <= n; ++i){
            fa[i] = i;
            sum[i] = 0;
        }
        int ans = 0;
        while (m--){
            scanf("%d%d%d", &l, &r, &s);
            l --;
            int pa = findFa(l), pb = findFa(r);
            if (pa == pb){
                if (sum[r] - sum[l] != s) ans++;
            }
            else {
                fa[pb] = pa;
                sum[pb] = sum[l] - sum[r] + s;
            }
        }
        printf("%d
", ans);
    }
    return 0;
}