sicily 4433 DAG?

题意：输入一个有向图，判断该图是否是有向无环图(Directed Acyclic Graph)。

解法：还是深搜

 #include<iostream>
 #include<memory.h>
 #include<stack>

 using namespace std;

 bool paths[][];
 int visited[];
 bool isDAG;
 int vertices,edges;

 void DFS(int current){
     for(int j =; isDAG == true && j <=vertices; j++){
         if(paths[current][j] == true){
             if(visited[j] == ){
                 visited[j] = ;
                 DFS(j);
             }
             else if(visited[j] == )
                 isDAG = false;
         }
     }
     //marked node as visted one stoping duplicated visiting when other visit trying to visit this pre-visit node
     visited[current] = -;
 }
 int main(){
     int from,dest;
     memset(paths,false,sizeof(paths));
     memset(visited,,sizeof(visited));
     cin >> vertices >> edges;
     for(int i=;i<= edges;i++){
         cin >> from >> dest;
         paths[from][dest] = true;
     }
     //depth-first search checking every node
     isDAG = true;
     for(int i=; isDAG == true && i <= vertices; i++){
         if(visited[i] == ){
             visited[i] == ;
             DFS(i);
         }
     }
     if(isDAG)
         cout <<  << endl;
     else
         cout <<  << endl;
     return ;
 }