● 647. 回文子串 ● 516.最长回文子序列

•  647. 回文子串  

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

•  516.最长回文子序列

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