944. Delete Columns to Make Sorted

Easy

You are given an array of n strings strs, all of the same length.

The strings can be arranged such that there is one on each line, making a grid. For example, strs = ["abc", "bce", "cae"] can be arranged as:

abc
bce
cae

You want to delete the columns that are not sorted lexicographically. In the above example (0-indexed), columns 0 ('a', 'b', 'c') and 2 ('c', 'e', 'e') are sorted while column 1 ('b', 'c', 'a') is not, so you would delete column 1.

Return the number of columns that you will delete.

Solution

class Solution:
    def minDeletionSize(self, strs: List[str]) -> int:
        res = 0

        for i in range(len(strs[0])):
            col = list(map(lambda s: s[i], strs))
            if sorted(col) != col:
                res += 1

        return res