图算法例题

图算法sicily例题 1000. sicily 1155. Can I Post the lette Time Limit: 1sec Memory Limit:32MB Description I am a traveler. I want to post a letter to Merlin. But because there are so many roads I can walk through, and maybe I can’t go to Merlin’s house following these roads, I must judge whether I can post the letter to Merlin before starting my travel. Suppose the cities are numbered from 0 to N-1, I am at city 0, and Merlin is at city N-1. And there are M roads I can walk through, each of which connects two cities. Please note that each road is direct, i.e. a road from A to B does not indicate a road from B to A. Please help me to find out whether I could go to Merlin’s house or not. Input There are multiple input cases. For one case, first are two lines of two integers N and M, (N<=200, M<=N*N/2), that means the number of citys and the number of roads. And Merlin stands at city N-1. After that, there are M lines. Each line contains two integers i and j, what means that there is a road from city i to city j. The input is terminated by N=0. Output For each test case, if I can post the letter print “I can post the letter” in one line, otherwise print “I can't post the letter”. Sample Input 3 2 0 1 1 2 3 1 0 1 0 Sample Output I can post the letter I can't post the letter Source Code #include <iostream> #include <vector> using namespace std; int n,m; vector<int> vout[200]; bool visited[200]; bool flood(int u) { visited[u]=1; if (u==n-1) return 1; for (int x=0; x<vout[u].size(); x++) { int &v=vout[u][x]; if (!visited[v] && flood(v)) return 1; } return 0; }