代码随想录day46 647. 回文子串 516.最长回文子序列

代码随想录day46 647. 回文子串 516.最长回文子序列

647. 回文子串

代码随想录

class Solution {
public:
    int countSubstrings(string s) {
        int size = s.size();
        vector<vector<bool>> dp(size, vector<bool>(size, false));
        int res = 0;
        for (int i = size - 1; i >= 0; i--) {
            for (int j = i; j < size; j++) {
                if (s[i] != s[j]) {
                    continue;
                }
                if (j - i <= 1 || dp[i + 1][j - 1]) {
                    res++;
                    dp[i][j] = true;
                    continue;
                }
            }
        }
        return res;
    }
};

516. 最长回文子序列

代码随想录

class Solution {
public:
    int longestPalindromeSubseq(string s) {
        int size = s.size();
        vector<vector<int>> dp(size, vector<int>(size, 0));
        for (int i = 0; i < size; i++) {
            dp[i][i] = 1;
        }
        for (int i = size - 1; i >= 0; i--) {
            for (int j = i + 1; j < size; j++) {
                if (s[i] == s[j]) {
                    dp[i][j] = dp[i + 1][j - 1] + 2;
                } else {
                    dp[i][j] = max(dp[i + 1][j], dp[i][j - 1]);
                }
            }
        }
        return dp[0][size - 1];
    }
};