LeetCode 1216. Valid Palindrome III Longest Palindromic Subsequence Valid Palindrome Valid Palindrome II

原题链接在这里：https://leetcode.com/problems/valid-palindrome-iii/

题目：

Given a string s and an integer k, find out if the given string is a K-Palindrome or not.

A string is K-Palindrome if it can be transformed into a palindrome by removing at most k characters from it.

Example 1:

Input: s = "abcdeca", k = 2
Output: true
Explanation: Remove 'b' and 'e' characters.

Constraints:

• 1 <= s.length <= 1000
• s has only lowercase English letters.
• 1 <= k <= s.length

题解：

Find the longest palindrome from s.

And check the difference between s and longest palindrome length, if it is <= k, then return true.

Time Complexity: O(n^2). n = s.length().

Space: O(n^2).

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AC Java:

 1 class Solution {
 2     public boolean isValidPalindrome(String s, int k) {
 3         if(s == null || s.length() <= k){
 4             return true;
 5         }
 6         
 7         int lp = findLongestPalin(s);
 8         return s.length() - lp <= k;
 9     }
10     
11     private int findLongestPalin(String s){
12         if(s == null || s.length() == 0){
13             return 0;
14         }
15         
16         int n = s.length();
17         int [][] dp = new int[n][n];
18         for(int i = n-1; i>=0; i--){
19             dp[i][i] = 1;
20             for(int j = i+1; j<n; j++){
21                 if(s.charAt(i) == s.charAt(j)){
22                     dp[i][j] = dp[i+1][j-1] + 2;
23                 }else{
24                     dp[i][j] = Math.max(dp[i+1][j], dp[i][j-1]);
25                 }
26             }
27         }
28         
29         return dp[0][n-1];
30     }
31 }

类似Longest Palindromic Subsequence, Valid Palindrome, Valid Palindrome II.