Course schedule

class Solution {
public:
    int dfs(vector<int> *a,vector<int> &vis,vector<int> &rec,int x)
    {
        vis[x]=1;
        rec[x]=1;
        for(int i:a[x])
        {
            if(vis[i]==1 && rec[i]==1)
                return 1;
            if(vis[i]==0 && dfs(a,vis,rec,i))
                return 1;
        }
        rec[x]=0;
        return 0;
    }
    bool canFinish(int n, vector<vector<int>>& e) {
        vector<int> a[n];
        for(int i=0;i<e.size();i++)
        {
            a[e[i][0]].push_back(e[i][1]);
        }
        vector<int> vis(n,0);
        vector<int> rec(n,0);
        for(int i=0;i<n;i++)
        {
            if(vis[i]==0)
            {
                int x=dfs(a,vis,rec,i);
                if(x==1)
                    return 0;
            }
        }
        return 1;
    }
};
// to complete all courses there shouldn't be any cycle
// if there is a cycle then we cannot complete all course