leetcode -- Search a 2D Matrix

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

• Integers in each row are sorted from left to right.
• The first integer of each row is greater than the last integer of the previous row.

 For example,

Consider the following matrix:

[
  [1,   3,  5,  7],
  [10, 11, 16, 20],
  [23, 30, 34, 50]
]

Given target = 3, return true.

public boolean searchMatrix(int[][] matrix, int target) {
        // Start typing your Java solution below
        // DO NOT write main() function
        int M = matrix.length;
        if(M == 0){
            return false;
        }
        int N = matrix[0].length;
        if(N == 0){
            return false;
        }
        
        int row = 0, col = N - 1;
        while(row < M && col >= 0){
            if(matrix[row][col] == target){
                return true;
            } else if(matrix[row][col] > target){
                col--;
            } else{
                row++;
            }
        }
        return false;
    }