POJ 2492 A Bug's Life

#include <iostream>
#include <cstdio>
#include <cstring>
#define REP(i, s, n) for(int i = s; i <= n; i ++)
#define REP_(i, s, n) for(int i = n; i >= s; i --)
#define MAX_N 2000 + 10

using namespace std;

int n, q, F[MAX_N];
int D[MAX_N];

int find(int x){
    if(x == F[x]) return x;
    return F[x] = find(F[x]);
}
void Union(int x,int y){
    x = find(x), y = find(y);
    if(x == y) return;
    F[y] = x;
}

int main(){
    int T; scanf("%d", &T);
    REP(k, 1, T){
        scanf("%d%d", &n, &q);
        REP(i, 1, n) F[i] = i, D[i] = 0;
        int x, y; bool ok = 1;
        while(q --){
            scanf("%d%d", &x, &y);
            if(find(x) != find(y)){
                if(!D[x] && !D[y]) D[x] = y, D[y] = x;
                else if(!D[x]) D[x] = y, Union(x, D[y]);
                else if(!D[y]) D[y] = x, Union(y, D[x]);
                else Union(x, D[y]), Union(y, D[x]);
            }
            else ok = 0;
        }
        printf("Scenario #%d:\n", k);
        if(!ok) printf("Suspicious bugs found!\n\n");
        else printf("No suspicious bugs found!\n\n");
    }
    return 0;
}