https://leetcode.com/problems/valid-palindrome-iii/description/
This is a counterpart question of 516. Longest Palindromic Subsequence.
Given the lenghth of the string is l, if we could find the length of Longest Palindromic Subsequence p, it means we at least need to delete l - p chars to get a palindrom.
Then we only need to check l - p <= k to answer if a string can be transformed into a palindrome by removing at most k characters from it.