LeetCode周赛#111 Q2 Delete Columns to Make Sorted

题目来源：https://leetcode.com/contest/weekly-contest-111/problems/delete-columns-to-make-sorted/

问题描述

 944. Delete Columns to Make Sorted

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. 1 <= A.length <= 100
2. 1 <= A[i].length <= 1000

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题意

给定一个由字符组成的二维数组，问删去多少列，可以使得剩下的每列都是字典序的。

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思路

依次判断二维数组的每列是否是字典序即可。不配LeetCode Medium的难度。

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代码

class Solution {
public:
    int minDeletionSize(vector<string>& A) {
        int n = A.size(), m = A[0].size(), i = 0, j = 0, ret = 0;
        for (i=0; i<m; i++)
        {
            for (j=0; j<n-1; j++)
            {
                if (A[j][i] > A[j+1][i])
                {
                    ret++;
                    break;
                }
            }
        }
        return ret;
    }
};