社交网络图中结点的“重要性”计算（并查集+bfs）

收获：

1.判断是否连通，用并查集

2.有多少层数 用bfs

代码：

#include <iostream>
#include <queue>
#include <cstring>
using namespace std;
 
#define N 10005
int map[N][N];
int visited[N] = {0};
int pre[N];
int n, m;
 
int find(int x) {
    if(x != pre[x])
        return pre[x] = find(pre[x]);
    return x;
}
 
void Union(int x, int y) {
    int a = find(x);
    int b = find(y);
    if(a != b)
        pre[a] = b;
}
 
int BFS(int s) {
    memset(visited, 0, sizeof(visited));
    visited[s] = 1;
    queue<int> q;
    q.push(s);
    int last = s;
    int tail;
    int level = 0;
    int cnt = 0;
    int sum = 0;
    while(!q.empty()) {
        int l = q.front();
        q.pop();
        for(int i = 1; i <= n; i++)
            if(!visited[i] && map[l][i]) {
                visited[i] = 1;
                q.push(i);
                c