OI-codes/S2OJ/106/data/val.cpp

#include <bits/stdc++.h>

#include "testlib.h"
using namespace std;

const int MAXN = 5005;
const int LIM = 3e5;
int f[MAXN];
int n, m, s, t;

inline int find(int x) {
    return f[x] != x ? f[x] = find(f[x]) : x;
}

inline void merge(int x, int y) {
    x = find(x);
    y = find(y);
    if (x ^ y) f[x] = y;
}

int main(int argc, char *argv[]) {
    registerValidation();

    n = inf.readInt(1, 2500);
    inf.readSpace();
    m = inf.readInt(1, min(n * (n - 1) / 2, 6200));
    inf.readSpace();
    s = inf.readInt(1, n);
    inf.readSpace();
    t = inf.readInt(1, n);
    inf.readEoln();

    for (int i = 1; i <= n; ++i) f[i] = i;

    for (int i = 1, u, v; i <= m; ++i) {
        u = inf.readInt(1, n);
        inf.readSpace();
        v = inf.readInt(1, n);
        inf.readSpace();
        inf.readInt(1, LIM);
        inf.readEoln();

        ensuref(u != v, "Self loop found!");
        merge(u, v);
    }

    inf.readEof();

    ensuref(find(s) == find(t), "The graph is not connected!");

    return 0;
}