palindrome-partitioning leetcode C++

Given a string s, partition s such that every substring of the partition is a palindrome.

Return all possible palindrome partitioning of s.

For example, given s ="aab", Return

[ ["aa","b"], ["a","a","b"] ]

C++

class Solution {
public:
    vector<vector<string>> partition(string s){
        vector<vector<string>> res;
        vector<string> out;
        partitionDFS(s,0,out,res);
        return res;
    }
    
    void partitionDFS(string s, int start, vector<string> &out, vector<vector<string>> &res) {
        if (start == s.size()) {
            res.push_back(out);
            return;
        }
        for (int i = start; i < s.size(); ++i) {
            if (isPalindrome(s, start, i)) {
                out.push_back(s.substr(start, i - start + 1));
                partitionDFS(s, i + 1, out, res);
                out.pop_back();
            }
        }
    }
    bool isPalindrome(string s, int start, int end) {
        while (start < end) {
            if (s[start] != s[end]) return false;
            ++start;
            --end;
        }
        return true;
    }
};