LintCode 136. 分割回文串

class Solution {
public:
    /*
     * @param s: A string
     * @return: A list of lists of string
     */
    bool isPalindromic(string &s){
         int i=0,j=s.length()-1;
         while(i<j){
             if(s[i++]!=s[j--])
                return false;
        }
         return true;
    }
    void dfs(vector<vector<string>> &ans,vector<string> &vec,string &s,int pos){
        if(pos==s.length()){
            ans.push_back(vec);
        }
        for(int i=pos;i<s.length();i++){
            string str=s.substr(pos,i-pos+1);
            if(isPalindromic(str)){
                vec.push_back(str);
                dfs(ans,vec,s,i+1);
                vec.pop_back();
            }

        }
    }
    vector<vector<string>> partition(string &s) {
        vector<vector<string> > ans;
        vector<string> vec;
        dfs(ans,vec,s,0);
        return ans;
    }
};