# 944. Delete Columns to Make Sorted

**<font color=red>难度: Medium</font>**

## 刷题内容

> 原题连接

* https://leetcode.com/problems/delete-columns-to-make-sorted/

> 内容描述

```
We are given an array A of N lowercase letter strings, all of the same length.

Now, we may choose any set of deletion indices, and for each string, we delete all the characters in those indices.

For example, if we have a string "abcdef" and deletion indices {0, 2, 3}, then the final string after deletion is "bef".

Suppose we chose a set of deletion indices D such that after deletions, each remaining column in A is in non-decreasing sorted order.

Formally, the c-th column is [A[0][c], A[1][c], ..., A[A.length-1][c]]

Return the minimum possible value of D.length.

 

Example 1:

Input: ["cba","daf","ghi"]
Output: 1
Example 2:

Input: ["a","b"]
Output: 0
Example 3:

Input: ["zyx","wvu","tsr"]
Output: 3
 

Note:

1 <= A.length <= 100
1 <= A[i].length <= 1000
```

## 解题方案

> 思路 1
******- 时间复杂度: O(m * n)******- 空间复杂度: O(1)******


比赛时候看错题目，无语。。注意这句话就行```Formally, the c-th column is [A[0][c], A[1][c], ..., A[A.length-1][c]]```


```python
class Solution:
    def minDeletionSize(self, A):
        """
        :type A: List[str]
        :rtype: int
        """
        res = 0
        for i in range(len(A[0])):
            flag = True
            for j in range(1, len(A)):
                if A[j][i] < A[j-1][i]:
                    flag = False
                    break
            if not flag:
                res += 1
        return res
```
