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;
}
