240 Search a 2D Matrix II

class Solution:
    # @param {integer[][]} matrix
    # @param {integer} target
    # @return {boolean}
    def searchMatrix(self, matrix, target):
        m = len(martix)
        if m == 0:
            return False
        n = len(matrix[0])
        i, j = m - 1, 0
        while i >= 0 and j < n:
            if matrix[i][j] == target:
                return True
            elif matrix[i][j] < target:
                j += 1
            else:
                i -= 1
        return False