九度OJ 題目1526：朋友圈(小米2013年校園招聘筆試題)

並查集。

題目：http://ac.jobdu.com/problem.php?pid=1526

#include <stdio.h>
#include <cmath>
#include <string.h>
#include <iostream>

using namespace std;
const int maxn = 100005;
int father[maxn];
int rank[maxn];
int flag[maxn];
int n,m;

void make_set(int n){
    for(int i = 1;i <= n;i++){
        father[i] = i;
        rank[i] = 0;
    }
}
int find_set(int x){
    if(father[x] == x)
        return x;
    return father[x] = find_set(father[x]);
}
void union_set(int x,int y){
    int xx = find_set(x);
    int yy = find_set(y);
    if(xx == yy) return;
    if(rank[xx] > rank[yy])
        father[yy] = xx;
    else{
        if(rank[xx] == rank[yy])
            rank[yy]++;
        father[xx] = y;
    }
}
int count_set(){
    int ans = 0;
    memset(flag,0,sizeof(flag));
    for(int i = 1;i <= n;i++){
        flag[find_set(i)]++;
        //printf("%d *\n",find_set(i));
    }
    for(int i = 1;i <= n;i++)
        if(flag[i])
            ans++;
    return ans;
}
int main(){
    while(~scanf("%d%d",&n,&m)&&n){
        make_set(n);
        int x,y;
        for(int i = 0;i < m;i++){
            scanf("%d%d",&x,&y);
            union_set(x, y);
        }
        printf("%d\n",count_set());
    }
    return 0;
}