HDU-1232 畅通工程

1、知识点：连通分量
2、思路：并查集

/*用途：**说明：**算法：并查集 *///#define LOCAL#include <cstdio>#include <string.h>using namespace std;#define MAXN 1000+10int N, M;int pre[MAXN];int block[MAXN];int find(int x);void uni(int x, int y);int main(){#ifdef LOCAL    freopen(".in", "r", stdin);    freopen(".out", "w", stdout);#endif    while(scanf("%d", &N) && N){        scanf("%d", &M);        for(int i=1; i<=N; i++)            pre[i] = i;        for(int i=1; i<=M; i++){            int a, b;            scanf("%d%d", &a, &b);            uni(a, b);        }        memset(block, 0, sizeof(block));        for(int i=1; i<=N; i++)            block[find(i)] = 1;        int ans = 0;        for(int i=1; i<=N; i++)            if(block[i])                ans++;        printf("%d\n", ans-1);    }    return 0;}inline int find(int x){    int top = x;    while(top != pre[top])        top = pre[top];    int temp;                   //暂时保存x以前的上级结点     while(pre[x] != top){       //路径压缩         temp = pre[x];        pre[x] = top;        x = temp;    }    return top;}inline void uni(int x, int y){    int fx, fy;    fx = find(x);    fy = find(y);    if(fx != fy)        pre[fx] = fy;}