拓撲排序代碼

#include <iostream>using namespace std;int map[104][104];int n;bool flag[104];void update(int x){for(int i=0;i<n;i++)map[x][i]=0;}bool Tsort(){for(int i=0;i<n;i++){bool ff=false;//判斷改圖是否為連通圖for(int j=0;j<n;j++){if(flag[j])continue;int sign=1;for(int k=0;k<n;k++)if(map[k][j]){sign=0;break;}if(sign){flag[j]=true;update(j);ff=true;break;}}if(!ff)return false;}for(int i=0;i<n;i++)//判斷該是否存在迴路（這個判斷如果去掉也正確）{if(!flag[i])return false;}return true;}int main(){int m,x,y;while(scanf("%d%d",&n,&m)&&n!=0){memset(map,0,sizeof(map));memset(flag,false,sizeof(flag));for(int i=0;i<m;i++){scanf("%d%d",&x,&y);map[x][y]=1;}if(Tsort())printf("YES\n");elseprintf("NO\n");}return 0;}