lc-longest-palindromic.cpp

class Solution {
public:
    string longestPalindrome(string s) {
        if(s.size() == 0) {
            return "";
        }
        if(s.size() == 1) {
            return s;
        }
        int start = 0;
        int end = 0;
        
        for(int i = 0; i < s.size(); i++) {
            // Verify centers of 1 and 2 letters, expand
            int singleC = expandCenter(s, i, i);
            int doubleC = expandCenter(s, i, i + 1);
            if(maxLen > end - start){
                start = i - (maxLen - 1) / 2;
                end = i + maxLen / 2;
            }
        }
        
        return s.substr(start, end - start + 1);
    }
private:
    int expandCenter(string s, int left, int right) {
        int L = left;
        int R = right;
        while(L >= 0 && R < s.size() && s[L] == s[R]) {
            L--;
            R++;
        }
        
        return R - L - 1;
    }
};