HDU 3038 How Many Answers Are Wrong

#include <cmath>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <iostream>
#include <fstream>
#include <string>
#include <vector>
#include <queue>
#include <stack>
#include <map>
#include <set>
#include <algorithm>
#include <functional>
#define  eps 1e-8
#define  pi  acos(-1.0)
#define  inf 0x3f3f3f3f
#define  INF 0x3f3f3f3f3f3f3f3fLL
#define  _clr(x,a) memset(x,a,sizeof(x))
#define  min(a,b)) (a)<(b)?(a):(b)
#define  max(a,b)  (a)>(b)?(a):(b)
#define  rep(i,n)  for(int i=1;i<=n;++i)
using namespace std;

//#define sponge_wxy_code

const int MAXN = 200010;
int parent[MAXN], sum[MAXN];
int n, m;

void init_set() {

    for(int i = 1; i <= n+1; ++i) {
        parent[i] = -1;
        sum[i] = 0;
    }
    return ;
}

int find_set(int u) {
    if(parent[u] < 0) return u;
    int temp = parent[u];
    parent[u] = find_set(parent[u]);
    sum[u] = sum[u] + sum[temp];
    return parent[u];
}

void union_set(int r1, int r2, int u, int v, int val) {

    if(r1 < r2) {
        sum[r2] = sum[u] + val - sum[v];
        parent[r1] += parent[r2];
        parent[r2] = r1;
    } else {
        sum[r1] = sum[v] - sum[u] - val;
        parent[r2] += parent[r1];
        parent[r1] = r2;
    }
    return ;
}

int main() {

#ifdef sponge_wxy_code
    freopen("aa.in",  "r", stdin);
    freopen("bb.out", "w", stdout);
#endif

    int u, v, val, ans;
    while(scanf("%d %d", &n, &m) != EOF) {
        init_set(); ans = 0;
        //rep(i, n) printf("%d ", parent[i]);
        //printf("\n");
        while(m--) {
            scanf("%d %d %d", &u, &v, &val); v++;
            int r1 = find_set(u), r2 = find_set(v);
            if(r1 == r2) {
                if(sum[v] - sum[u] != val)
                    ans++;
            } else {
                union_set(r1, r2, u, v, val);
            }
        }
        printf("%d\n", ans);
    }
    return 0;
}