NC_17_getLongestPalindrome
package org.example.interview.practice; /** * @author xianzhe.ma * @date 2021/9/3 */ public class NC_17_getLongestPalindrome { public static int getLongestPalindrome(String A, int n) { // write code here if (n < 2) return A.length(); //start表示最长回文串开始的位置, //maxLen表示最长回文串的长度 int maxLen = 1; boolean[][] dp = new boolean[n][n]; for (int right = 1; right < n; right++) { for (int left = 0; left <= right; left++) { //如果两种字符不相同,肯定不能构成回文子串 if (A.charAt(left) != A.charAt(right)) continue; //下面是s.charAt(left)和s.charAt(right)两个 //字符相同情况下的判断 //如果只有一个字符,肯定是回文子串 if (right == left) { dp[left][right] = true; } else if (right - left <= 2) { //类似于"aa"和"aba",也是回文子串 dp[left][right] = true; } else { //类似于"a******a",要判断他是否是回文子串,只需要 //判断"******"是否是回文子串即可 dp[left][right] = dp[left + 1][right - 1]; } //如果字符串从left到right是回文子串,只需要保存最长的即可 if (dp[left][right] && right - left + 1 > maxLen) { maxLen = right - left + 1; } } } //最长的回文子串 return maxLen; } public static int getLongestPalindrome(String input) { int length = input.length(); boolean[][] dp = new boolean[length][length]; int maxLen = 1; for (int right = 1;right < length;right++) { for (int left = 0;left <= right;left ++) { if (input.charAt(right) != input.charAt(left)) { continue; } if (left == right) { dp[left][right] = true; } else if (right - left <= 2) { dp[left][right] = true; } else { dp[left][right] = dp[left+1][right-1]; } //如果字符串从left到right是回文子串,只需要保存最长的即可 if (dp[left][right] && right - left + 1 > maxLen) { maxLen = right - left + 1; } } } return maxLen; } public static void main (String[] args) { String str = "baabccc"; // System.out.println(getLongestPalindrome(str, 7)); System.out.println(getLongestPalindrome(str)); } }