944. Delete Columns to Make Sorted

Posted 2021-06-06 Keep Learning

package LeetCode_944

/**
 * 944. Delete Columns to Make Sorted
 * https://leetcode.com/problems/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.

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:
1. n == strs.length
2. 1 <= n <= 100
3. 1 <= strs[i].length <= 1000
strs[i] consists of lowercase English letters.
 * */
class Solution {
    /*
    * solution: brute force, Time:O(n^2), Space:O(1)
    * */
    fun minDeletionSize(strs: Array<String>): Int {
        var needDeleteCount = 0
        val cols = strs[0].length
        for (i in 0 until cols) {
            for (j in 1 until strs.size) {
                if (strs[j][i] < strs[j-1][i]) {
                    needDeleteCount++
　　　　　　　　　　　　break

                }
            }
        }

        return needDeleteCount
    }
}