Problem URL: Delete columns to make sorted

We will iterate over the columns and for each column we will check if the column is sorted. If it is not, we will increment the number of columns to delete. Finally, we will return the number of columns to delete.

class Solution:
    def minDeletionSize(self, strs: List[str]) -> int:
        res = 0
        for col in zip(*strs):
            if any(col[i] > col[i+1] for i in range(len(col)-1)):
                res += 1
        return res

Time complexity: O(nm)
Space complexity: O(1)

We can achieve the same result with a single loop:

class Solution:
    def minDeletionSize(self, strs: List[str]) -> int:
        res = 0
        for col in zip(*strs):
            if col != tuple(sorted(col)):
                res += 1
        return res