Leetcode_944_Delete_Columns_to_Make_Sorted.py

"""
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 follows:
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.

 

Example 1:

Input: strs = ["cba","daf","ghi"]
Output: 1
Explanation: The grid looks as follows:
  cba
  daf
  ghi
Columns 0 and 2 are sorted, but column 1 is not, so you only need to delete 1 column.
Example 2:

Input: strs = ["a","b"]
Output: 0
Explanation: The grid looks as follows:
  a
  b
Column 0 is the only column and is sorted, so you will not delete any columns.
Example 3:

Input: strs = ["zyx","wvu","tsr"]
Output: 3
Explanation: The grid looks as follows:
  zyx
  wvu
  tsr
All 3 columns are not sorted, so you will delete all 3.
 

Constraints:

n == strs.length
1 <= n <= 100
1 <= strs[i].length <= 1000
strs[i] consists of lowercase English letters.
"""

class Solution:
    def minDeletionSize(self, strs: List[str]) -> int:
        n_rows, n_cols, n_del = len(strs), len(strs[0]), 0
        for j in range(n_cols):
            col_sorted = True
            for i in range(n_rows-1):
                if strs[i][j]>strs[i+1][j]:
                    col_sorted = False
                    break
            if not col_sorted:
                n_del += 1
        return n_del