刚开始从0开始找。。TL了，换成从n-1开始找。AC了。。
#include <iostream> #include <cstring> using namespace std; bool adj[200][200]; bool isVis[200]; int n; bool dfs(int cur) { if(cur == 0) return true; for(int i = 0; i < n; i++) { if(!isVis[i] && adj[cur][i]) { isVis[i] = true; if(dfs(i)) return true; isVis[i] = false; } } return false; } int main() { int m; while(cin >> n && n != 0) { cin >> m; memset(adj, false, sizeof(adj)); memset(isVis, false, sizeof(isVis)); for(int i = 0; i < m; i++) { int a, b; cin >> a >> b; adj[b][a] = true; } isVis[n - 1] = true; if(dfs(n - 1)) cout << "I can post the letter/n"; else cout << "I can't post the letter/n"; } return 0; }
