Write an efficient algorithm that searches for a value in anmxnmatrix. This matrix has the following properties:

• Integers in each row are sorted in ascending from left to right.
• Integers in each column are sorted in ascending from top to bottom.

For example,

Consider the following matrix:

[
  [1,   4,  7, 11, 15],
  [2,   5,  8, 12, 19],
  [3,   6,  9, 16, 22],
  [10, 13, 14, 17, 24],
  [18, 21, 23, 26, 30]
]

Giventarget=5, returntrue.

Giventarget=20, returnfalse.

class Solution {
    public boolean searchMatrix(int[][] matrix, int target) {
        if (matrix == null || matrix.length == 0) return false;
        int n = matrix.length, m = matrix[0].length;

        int x = 0, y = m - 1;

        while (x < n && y >= 0){
            if (matrix[x][y] > target){
                y--;
            }
            else if (matrix[x][y] < target){
                x++;
            }
            else{
                return true;
            }
        }

        return false;
    }
}