【剑指】二维数组中的查找

class Solution:
    def findNumberIn2DArray(self, matrix: List[List[int]], target: int) -> bool:
        if not matrix: return False
        m, n = len(matrix),len(matrix[0])
        i,j = 0, n-1
        while i<m and j>=0:
            if matrix[i][j]>target:
                j-=1
            elif matrix[i][j]<target:
                i+=1
            else:
                return True
        return False