Coding Caprice - dynamic programming13

647. 回文子串

class Solution {
public:
    int countSubstrings(string s) {
        int s_len = s.size();
        vector<int> dp{0};
        int out(1);
        for(int i=1; i<s_len; ++i){
            out++;
            vector<int> dq{i};
            if(s[i]==s[i-1]){
                dq.push_back(i-1);
                out++;
            }
            for(int j:dp){
                if(j>0&&s[j-1]==s[i]){
                    dq.push_back(j-1);
                    out++;
                }
            }
            swap(dp, dq);
         }
         return out;
    }
};

• 搞笑了

516. 最长回文子序列

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