hdu 3038 How Many Answers Are Wrong(并查集)

题目链接：hdu 3038 How Many Answers Are Wrong

题目大意：略。

解题思路：并查集水题。

#include <cstdio>
#include <cstring>
#include <iostream>

using namespace std;

typedef long long ll;
const int N = 200005;
//const ll UFmod = 0x3f3f3f3f3f;

struct UFset {
    int root;
    int parent;
    ll value;
}U[N];

int UFfind(int x) {
    if (U[x].root == 0) {
        int tmp = U[x].parent;
        U[x].parent = UFfind(U[x].parent);
// U[x].value = (U[x].value + U[tmp].value) % UFmod;
        U[x].value = U[x].value + U[tmp].value;
        return U[x].parent;
    } else
        return x;
}

void UFunion(int x, int y, int p, int q, ll type) {
    U[p].parent += U[q].parent;

    U[q].parent = p;
    U[q].root = 0;
// U[q].value = (U[x].value + type + UFmod - U[y].value) % UFmod;
    U[q].value = (U[x].value + type - U[y].value);
}

void UFinit (int n) {
    for (int i = 0; i <= n; i++) {
        U[i].parent = 1;
        U[i].value = 0;
        U[i].root = 1;
    }
}

int n, m;

int main () {
    while (scanf("%d%d", &n, &m) == 2) {
        UFinit(n);
        int a, b, ans = 0;
        ll c;
        for (int i = 0; i < m; i++) {
            scanf("%d%d", &a, &b);
            cin >> c;
            a--;
            int p = UFfind(a), q = UFfind(b);

            if (p == q) {
                if (U[a].value + c != U[b].value)
                    ans++;
            } else {
                UFunion(a, b, p, q, c);
            }
        }
        printf("%d\n", ans);
    }
    return 0;
}