今日任务

647. 回文子串

516.最长回文子序列

647. 回文子串

题目链接： . - 力扣（LeetCode）

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

516.最长回文子序列

题目链接：

class Solution {
    public int longestPalindromeSubseq(String s) {
        if (s.length() == 1) return 1;
        int[][] dp = new int[s.length()][s.length()];

        for (int i = s.length() - 1; i >= 0; i--) {
            dp[i][i] = 1;
            for (int j = i + 1; j < s.length(); 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][j - 1], dp[i + 1][j]);
                }
            }
        }
        return dp[0][s.length() - 1];
    }
}