Problem URL: Sum in a matrix

We will iterate over each row and sort them. Then we iterate over each column and get the maximum value of the column. Finally, we return the sum of the maximum values.

class Solution:
    def matrixSum(self, nums: List[List[int]]) -> int:
        ROWS, COLS = len(nums), len(nums[0])
        res = 0

        for num in nums:
            num.sort()

        for c in range(COLS):
            _max = -math.inf
            for r in range(ROWS):
                _max = max(_max, nums[r][c])
            res += _max

        return res

Time complexity: O(nmlog(m)) where n is the number of rows and m is the number of columns.
Space complexity: O(1)

We can achieve the same result with just 1 line of code in python.

class Solution:
    def matrixSum(self, nums: List[List[int]]) -> int:
        return sum(map(max, zip(*map(sorted, nums))))