1155. Can I Post the letter
Constraints
Time Limit: 1 secs, Memory Limit: 32 MB
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
利用Dijiskra算法解决问题
#include<iostream> #include<memory> using namespace std; const int MAX = 205; int edge[MAX][MAX]; bool visited[MAX]; int n, m; void DFS(int current) { for(int i=0;i<n;i++) { if(!visited[i]&&edge[current][i]) { visited[i]=true; DFS(i); } } } int main() { while(cin>>n&&n!=0&&cin>>m) { memset(edge, 0, sizeof(edge)); memset(visited, false, sizeof(visited)); int a, b; for(int i=0;i<m;i++) { cin>>a>>b; edge[a][b]=1; edge[b][a]=1; } visited[0]=true; DFS(0); if(visited[n-1])cout<<"I can post the letter "; else cout<<"I can't post the letter "; } return 0; }