bool searchMatrix(vector<vector<int> >& matrix, int target){
            int n = matrix.size();
            if(n == 0)
                return false;
            int m = matrix[0].size();
            if(m == 0)
                return false;
            int l = 0;
            int r = n;
            int row = n/2;
            int next_row = row+1;
            while(next_row < n && !(matrix[row][0] <= target && matrix[next_row][0] >= target)){
                if(target > matrix[row][0]){
                      l = row;
                      row = (row + r)/2;
                }
                else{
                    r = row;
                    row = (l+row)/2;
                }
                next_row = row+1;
            }
            if(next_row >= n){
                return binary_search(matrix[row].begin(),matrix[row].end(),target);
            }
            if(matrix[next_row][0] == target)
                return true;
            else{
                return binary_search(matrix[row].begin(),matrix[row].end(),target);
            }
        }