<p>Given a string <code>s</code>, partition <code>s</code> such that every <span data-keyword="substring-nonempty">substring</span> of the partition is a <span data-keyword="palindrome-string"><strong>palindrome</strong></span>. Return <em>all possible palindrome partitioning of </em><code>s</code>.</p>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>
<pre><strong>Input:</strong> s = "aab"
<strong>Output:</strong> [["a","a","b"],["aa","b"]]
</pre><p><strong class="example">Example 2:</strong></p>
<pre><strong>Input:</strong> s = "a"
<strong>Output:</strong> [["a"]]
</pre>
<p>&nbsp;</p>
<p><strong>Constraints:</strong></p>

<ul>
	<li><code>1 &lt;= s.length &lt;= 16</code></li>
	<li><code>s</code> contains only lowercase English letters.</li>
</ul>

class Solution {
public:
    vector<vector<string>> partition(string s) {
        vector<vector<string>> res;
        vector<string> curr;
        helper(s, 0, curr, res);
        return res;
    }

    void helper(string s, int index, vector<string>& curr, vector<vector<string>>& res) {
        int size = curr.size();
        if (index >= s.size()) {
            if (checkPalindrome(curr[size-1])) {
                vector<string> temp = curr;
                res.push_back(temp);
            }
            return;
        }

        // take index into current partition
        if (size > 0) {
            string temp = curr[size-1];
            curr[size-1] = curr[size-1] + s[index];
            helper(s, index + 1, curr, res);
            curr[size-1] = temp;
        }
        
        // split and take index into next partition
        // check if current partition is a palindrome
        if (size == 0 || (size > 0 && checkPalindrome(curr[size-1]))) {
            curr.push_back(string {s[index]});
            helper(s, index + 1, curr, res);
            curr.pop_back();
        }
    }

    bool checkPalindrome(string s) {
        int n = s.size();
        for (int i = 0; i < s.size(); i++) {
            if (s[i] != s[n-i-1])
                return false;
        }
        return true;
    }
};
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