杭电OJ：畅通工程

#include <stdio.h>
#include <stdlib.h>
#include <memory.h>

int father[10005];
bool arr[10005];

void init () {
    for (int i=0; i<1000; i++) {
        father[i] = i;
    }
}

int find (int x) {//查找并压缩路径
    return father[x] == x ? x : father[x] = find(father[x]);
}

void join (int x, int y) {
    int p1 = find(x);
    int p2 = find(y);

    if (p1 == p2) {
        return;
    }

    father[p1] = p2;
}

bool check (int x, int y) {
    int p1 = find(x);
    int p2 = find(y);

    if (p1 == p2) {
        return true;
    }
    else {
        return false;
    }
}

int main (int argc, char **argv) {
    int m, n;
    int a, b;
    int ans;
    while (scanf("%d",&m)) {//m城镇,n道路
        if (m == 0) { break; }
        scanf("%d", &n);
        init();
        ans = 0;
        for (int i=1; i <= n; i++) {
            scanf("%d %d", &a, &b);
            join(a, b);
        }
        memset(arr, 0, sizeof(arr));
        for (int i=1; i <= m; i++) {
            arr[find(i)] = 1;
        }
        for (int i=1; i <= m; i++) {
            if (arr[i]) {
                ans++;
            }
        }
        printf("%d\n", ans - 1);
    }
    return 0;
}