判断图是否有环

//判断邻接矩阵是否有环
bool judge(vector<vector<int>> path,int n){
    bool index = 0;
    while(1){
        index = 1;
        for(int i=0;i<n;i++){
            int sum = 0;
            for(int j=0;j<n;j++){
                sum+=path[i][j];
            }
            if(sum==1){
                //只连着一条边
                index = 0;
                for(int j=0;j<n;j++){
                    path[i][j] = 0;
                    path[j][i] = 0;
                }
            }
        }
        if(index==1) break;
    }
    int sum = 0;
    for(int i=0;i<n;i++) {

        for (int j = 0; j < n; j++) {
            sum += path[i][j];
        }
    }
    if(sum>0) return true;
    else return false;
}