Search a 2D matrix II

Time: O(M + N); Space: O(1); medium

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

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]
]

Example 1:

Input: target = 5

Output: True

Example 2:

Input: target = 20

Output: False

[1]:

class Solution1(object):
    def searchMatrix(self, matrix, target):
        """
        :type matrix: int[][]
        :type target: int
        :rtype: boolean
        """
        m = len(matrix)
        if m == 0:
            return False

        n = len(matrix[0])
        if n == 0:
            return False

        count, i, j = 0, 0, n - 1
        while i < m and j >= 0:
            if matrix[i][j] == target:
                return True
            elif matrix[i][j] > target:
                j -= 1
            else:
                i += 1

        return False

[2]:

s = Solution1()
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]
         ]
target = 5
assert s.searchMatrix(matrix, target) == True
target = 20
assert s.searchMatrix(matrix, target) == False