[HDU 1232 ]畅通工程

基础并查集。

#include <cstdio>
#include <cstring>
#define maxn 1000 + 5
using namespace std;
int p[maxn];
void init(int n){
    for (int i = 1; i <= n; i++) p[i] = i;
}
int Find(int x){
    return p[x] == x ? x : (p[x] = Find(p[x]));
}
void Join(int x, int y){
    int fx = Find(x), fy = Find(y);
    if (fx != fy) p[fx] = fy;
}

int main(){
    int n, m;
    while (scanf("%d", &n) && n){
        scanf ("%d", &m);
        init(n);
        for (int i = 0; i < m; i++){
            int temp1, temp2;
            scanf("%d %d", &temp1, &temp2);
            Join(temp1, temp2);
        }
        int ans = 0;
        for (int i = 1; i <= n; i++) if (Find(i) == i) ans++;
        printf("%d\n", ans - 1);
    }

    return 0;
}