Delete Columns to Make Sorted II

arraystringgreedy

Problem Statement

You are given an array of n strings strs , all of the same length.

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

For example, if we have strs = ["abcdef","uvwxyz"] and deletion indices {0, 2, 3} , then the final array after deletions is ["bef", "vyz"] .

Suppose we chose a set of deletion indices answer such that after deletions, the final array has its elements in lexicographic order (i.e., strs[0] <= strs[1] <= strs[2] <= ... <= strs[n - 1] ). Return the minimum possible value of answer.length .

Examples

Example 1

Input: strs = ["ca","bb","ac"]
Output: 1
After deleting the first column, strs = ["a", "b", "c"].
Now strs is in lexicographic order (ie. strs[0] <= strs[1] <= strs[2]).
We require at least 1 deletion since initially strs was not in lexicographic order, so the answer is 1.

Example 2

Input: strs = ["xc","yb","za"]
Output: 0
strs is already in lexicographic order, so we do not need to delete anything.
Note that the rows of strs are not necessarily in lexicographic order:
i.e., it is NOT necessarily true that (strs[0][0] <= strs[0][1] <= ...)

Example 3

Input: strs = ["zyx","wvu","tsr"]
Output: 3
We have to delete every column.

Constraints

n == strs.length

1 <= n <= 100

1 <= strs[i].length <= 100

strs[i] consists of lowercase English letters.

🤔

Medium

Difficulty

Topic Info

ModuleDSA

CategoryArray

Sub-topicString