valid path

int dx[8] = {1,1,1,0,0,-1,-1,-1};
int dy[8] = {0,1,-1, 1,-1,0,1,-1};

string Solution::solve(int x, int y, int n, int r, vector<int> &X, vector<int> &Y) {

    vector< vector<bool>> mat(x+1, vector<bool>(y+1));

    for(int i = 0; i<=x; i++)
    {
        for(int j = 0; j<=y; j++)
        {
            bool flag = false;
            for(int k = 0; k<X.size(); k++)
            {
                if((X[k] - i)*(X[k] - i) + (Y[k] - j)*(Y[k] - j) <= r*r )
                {
                flag = true;
                break;
                }
            }

             mat[i][j] = flag;
        }
    }

    queue<pair<int, int>> q;

    if(mat[0][0] = true) return "NO";
    if(mat[x][y] = true) return "NO";

    q.push({0,0});
    mat[0][0] = true;

    while(!q.empty())
    {
        pair<int, int> top = q.front();
        q.pop();

        if(top.first == x && top.second == y) return "YES";

        for(int i = 0; i<8; i++)
        {
            int x1 = dx[i] + top.first;
            int y1 = dy[i] + top.second;

            if(x1<=x && y1<=y && x1>=0 && y1>=0 && mat[x1][y1] == false) {
                q.push({x1, y1});
                mat[x1][y1] = true;
            }
        }


    }


    return "NO";



}