德化住房和城乡建设网站竞价培训课程

代码随想录算法训练营Day59|动态规划17

一、647. 回文子串

class Solution {public int countSubstrings(String s) {boolean[][] dp = new boolean[s.length()][s.length()];int res = 0;for (int i = s.length() - 1; i >= 0; i--) {for (int j = i; j < s.length(); j++) {if (s.charAt(i) == s.charAt(j) && (j - i <= 1 || dp[i + 1][j - 1])) {res++;dp[i][j] = true;}}}return res;}
}

二、516.最长回文子序列

class Solution {public int longestPalindromeSubseq(String s) {int len = s.length();int[][] dp = new int[len + 1][len + 1];for (int i = len - 1; i >= 0; i--) { // 从后往前遍历 保证情况不漏dp[i][i] = 1; // 初始化for (int j = i + 1; j < len; j++) {if (s.charAt(i) == s.charAt(j)) {dp[i][j] = dp[i + 1][j - 1] + 2;} else {dp[i][j] = Math.max(dp[i + 1][j], Math.max(dp[i][j], dp[i][j - 1]));}}}return dp[0][len - 1];}
}