leetcode 944. Delete Columns to Make Sorted（python）

描述

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.

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.

Note:

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

解析

根据题意，将 strs 中的每个字符串按行排列，只要某一列的字符不符合升序规则就将该列移除，统计移除的次数即可。

解答

class Solution(object):
    def minDeletionSize(self, strs):
        """
        :type strs: List[str]
        :rtype: int
        """
        m = len(strs)
        n = len(strs[0])
        res = 0
        for i in range(n):
            for j in range(1,m):
                if strs[j-1][i]>strs[j][i]:
                    res += 1
                    break
        return res       	      

运行结果

Runtime: 172 ms, faster than 64.76% of Python online submissions for Delete Columns to Make Sorted.
Memory Usage: 14.4 MB, less than 95.24% of Python online submissions for Delete Columns to Make Sorted.

原题链接：https://leetcode.com/problems/delete-columns-to-make-sorted/

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