4.2.cpp

#include <iostream>
#include <queue>
#include <cstring>
#include <cstdio>
using namespace std;

const int maxn = 100;
bool g[maxn][maxn], visited[maxn];
int n;
queue<int> q;

void init(){
    memset(g, false, sizeof(g));
    memset(visited, false, sizeof(visited));
}
bool route(int src, int dst){
    q.push(src);
    visited[src] = true;
    while(!q.empty()){
        int t = q.front();
        q.pop();
        if(t == dst) return true;
        for(int i=0; i<n; ++i)
            if(g[t][i] && !visited[i]){
                q.push(i);
                visited[i] = true;
            }
    }
    return false;
}
int main(){
    freopen("4.2.in", "r", stdin);

    init();
    int m, u, v;
    cin>>n>>m;
    for(int i=0; i<m; ++i){
        cin>>u>>v;
        g[u][v] = true;
    }
    cout<<route(0, 6)<<endl;
    fclose(stdin);
    return 0;
}