hdu1269 迷宫城堡强连通分量

Posted 2022-11-23

题目链接：​​http://acm.hdu.edu.cn/showproblem.php?pid=1269​​​
题意：中文题
解析：判断强连通分量是否为1

#include <bits/stdc++.h>
using namespace std;
const int maxn = 1e4+100;
vector<int>G[maxn];
vector<int>rG[maxn];
vector<int>vs;
int vis[maxn];
int cmp[maxn];
void addEdge(int from,int to)

    G[from].push_back(to);
    rG[to].push_back(from);

void dfs(int u)

    vis[u] = 1;
    for(int i=0;i<(int)G[u].size();i++)
    
        int v = G[u][i];
        if(!vis[v])
            dfs(v);
    
    vs.push_back(u);

void rdfs(int u,int k)

    vis[u] = 1;
    cmp[u] = k;
    for(int i=0;i<(int)rG[u].size();i++)
    
        int v = rG[u][i];
        if(!vis[v])
            rdfs(v,k);
    

int scc(int n)

    memset(vis,0,sizeof(vis));
    vs.clear();
    for(int i=1;i<=n;i++)
    
        if(!vis[i])
            dfs(i);
    
    memset(vis,0,sizeof(vis));
    int k = 0;
    for(int i=vs.size()-1;i>=0;i--)
    
        if(!vis[vs[i]])
            rdfs(vs[i],k++);
    
    return k;

int main(void)

    int n,m;
    while(~scanf("%d %d",&n,&m))
    
        if(n==0&&m==0) break;
        for(int i=0;i<=n;i++)
            G[i].clear(),rG[i].clear();
        for(int i=0;i<m;i++)
        
            int x,y;
            scanf("%d %d",&x,&y);
            addEdge(x,y);
        
        if(scc(n)==1)
            puts("Yes");
        else
            puts("No");
    
    return 0;