PAT T1014 Circles of Friends

Posted 2021-03-10 zhanglichen

大水题，dfs判连通块的数量，bfs每个点找朋友圈的最大直径~

#include<bits/stdc++.h>
using namespace std;
const int maxn=1014;
vector<int> g[maxn];
bool visit[maxn];
int N;
int maxdepth=0;
void dfs (int s) {
    visit[s]=true;
    for (int i=0;i<g[s].size();i++) 
    if (visit[g[s][i]]==false) dfs(g[s][i]);
}
int dfsTrave () {
    int block=0;
    for (int i=1;i<=N;i++) 
    if (visit[i]==false) dfs(i),block++;
    return block;
}
void bfs (int s) {
    int depth[maxn]={0};
    queue<int> q;
    fill (visit,visit+maxn,false);
    q.push(s);
    visit[s]=true;
    while (!q.empty()) {
        int now=q.front();
        q.pop();
        for (int i=0;i<g[now].size();i++) 
        if (visit[g[now][i]]==false) {
            q.push(g[now][i]);
            depth[g[now][i]]=depth[now]+1;
            visit[g[now][i]]=true;
            maxdepth=max(maxdepth,depth[g[now][i]]);
        }
    }
}
int main () {
    scanf ("%d",&N);
    int k,x;
    for (int i=1;i<=N;i++) {
        scanf ("%d",&k);
        for (int j=1;j<=k;j++) {
            scanf ("%d",&x);
            g[i].push_back(x);
            g[x].push_back(i);
        }
    }
    int block=dfsTrave();
    for (int i=1;i<=N;i++) bfs (i);
    printf ("%d %d",block,max(0,maxdepth-1));
    return 0; 
}