LeetCode 944. 删列造序

删列造序

给你由 n 个小写字母字符串组成的数组 strs，其中每个字符串长度相等。这些字符串可以每个一行，排成一个网格。例如，strs = ["abc", "bce", "cae"] 可以排列为：

abc
bce
cae

你需要找出并删除 不是按字典序升序排列的 列。在上面的例子（下标从 0 开始）中，列 0（'a', 'b', 'c'）和列 2（'c', 'e', 'e'）都是按升序排列的，而列 1（'b', 'c', 'a'）不是，所以要删除列 1 。返回你需要删除的列数。

Delete Columns to Make Sorted

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.

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.

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.

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.

• n == strs.length
• 1 <= n <= 100
• 1 <= strs[i].length <= 1000
• strs[i] 由小写英文字母组成 / strs[i] consists of lowercase English letters.

这个题的话是给我们一个矩阵，然后让我们判断一下不是单调递增的然后输出列数，所以这个题目直接模拟一遍就可以了，然后是代码怎么写：

class Solution {
public:
    int minDeletionSize(vector<string>& strs) {
        // n的话代表列数，m的话代表行数
        int n=strs.size(),m=strs[0].size();
        // 定义一下答案
        int res=0;
        // 然后我们枚举一下所有列
        for(int i=0;i<m;i++) {
            // 然后判断一下它是不是递增的
            bool flag=true;
            // 从这一层第一行开始
            for(int j=1;j<n;j++) {
                // 如果我们发现第j行第i列是小于第j-1行第i列
                if(strs[j][i]<strs[j-1][i])
                    // 说明它不是单调递增的
                    flag=false;
                // 然后我们判断一下如果flag是true的话，说明这一行是单调递增的
                // 反之则不是单调递增的
                // 这题是问我们有多少列不是单调递增的
            }
            if(!flag) res++;
        }
        return res;
    }
};

func minDeletionSize(strs []string) int {
    res:=0
    n,m:=len(strs),len(strs[0])
    for i:=0;i<m;i++ {
        for j:=1;j<n;j++ {
            if strs[j][i]<strs[j-1][i] {
                res++
                break
            }
        }
    }
    return res
}