算法训练营笔记day57|647. 回文子串、516. 最长回文子序列

647. 回文子串

题目连接

笔记

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

516. 最长回文子序列

题目连接

笔记

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