leetcode---palindrome-partitioning---dp, dfs

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”]
]

class Solution {public:    vector< vector<bool> > ok;    void dfs(vector< vector<string> > &ans, vector<string> tmp, int dep, int n, const string &s)    {        if(dep >= n)        {            ans.push_back(tmp);        }        for(int j=dep; j<n; j++)        {            if(ok[dep][j])            {                tmp.push_back(s.substr(dep, j-dep+1));                dfs(ans, tmp, j+1, n, s);                tmp.pop_back();            }        }    }    vector<vector<string>> partition(string s)     {        int n = s.size();        ok = vector< vector<bool> >(n, vector<bool>(n, false));        for(int i=n-1; i>=0; i--)        {            for(int j=i; j<n; j++)            {                if(s[i] == s[j] && (i+1 >= j-1 || ok[i+1][j-1]))                    ok[i][j] = true;            }        }        vector< vector<string> > ans;        vector<string> tmp;        dfs(ans, tmp, 0, n, s);        return ans;    }};