4层循环暴力超时 

class Solution:
    def kthLargestValue(self, matrix: List[List[int]], k: int) -> int:
        nums=[]
        for a in range(len(matrix)):
            for b in range(len(matrix[0])):
                num=0
                for i in range(a+1):
                    for j in range(b+1):
                        num^=matrix[i][j]
                nums.append(num)
        nums.sort()
        return nums[-k]

使用前缀异或矩阵，再矩阵转列表 

class Solution:
    def kthLargestValue(self, matrix: List[List[int]], k: int) -> int:
        #前缀矩阵
        nums=matrix
        for a in range(len(matrix)):
            for b in range(len(matrix[0])):
                if a==0 and b==0:
                    nums[a][b]=matrix[a][b]
                elif a==0:
                    nums[a][b]=matrix[a][b]^nums[a][b-1]
                elif b==0:
                    nums[a][b]=matrix[a][b]^nums[a-1][b]
                else:
                    nums[a][b]=matrix[a][b]^nums[a][b-1]^nums[a-1][b]^nums[a-1][b-1]
        ret=[]
        #前缀矩阵转列表再排序
        for i in range(len(matrix)):
            for j in range(len(matrix[0])):
                ret.append(matrix[i][j])
        ret.sort()
        return ret[-k]