hdu 1232 畅通工程(数据结构:并查集)

并查集+路径压缩

注意城市编号从1到n,如果初始化时从0到n-1就坑了!!!

代码如下:

#include <cstdio>#include <iostream>#define LL long long#define MAXN 10010using namespace std;int p[MAXN];int find(int x) {    return x==p[x] ? x : p[x] = find(p[x]);}int main(void) {    int n, m, i, x, y;    LL cnt;    while(scanf("%d", &n) && n) {        scanf("%d", &m);        for(i=1; i<=n; ++i)            p[i] = i;        for(i=0; i<m; ++i) {            scanf("%d%d", &x, &y);            x = find(x);            y = find(y);            if(x != y)                 p[x] = y;        }        cnt = 0;        for(i=1; i<=n; ++i)            if(p[i] == i)                cnt++;        cout << cnt-1 << endl;    }    return 0;}