Restore IP Addresses

Given a string containing only digits, restore it by returning all possible valid IP address combinations.

For example:
Given "25525511135",

return ["255.255.11.135", "255.255.111.35"]. (Order does not matter)

深度优先遍历的思想，类似的题目还有：

1.Word Search

2.Word SearchII

3.Permutations,PermutationsII

4.Letter Combinations of a Phone Number

5.Unique Paths

6.Subsets,SubsetsII

class Solution {
public:void dfs(string& s,int sSize,int startPos,vector<string>& res,string oneOfRes,int k)
    {
        for(int i=startPos;(i<sSize) && (i<startPos+3) ;i++){
            if(i!=startPos && s[startPos]=='0'){
                return;
            }
            string tmpStr = s.substr(startPos,i-startPos+1);
            int value = stoi(tmpStr);
            if(value>255){
                return;    
            } 
            string tmpOneOfRes = oneOfRes;
            oneOfRes.empty()? oneOfRes += tmpStr : oneOfRes += "."+tmpStr;
            if(k+1<4){
                dfs(s,sSize,i+1,res,oneOfRes,k+1);
            }else{
                if(i+1==sSize){
                    if(find(res.begin(),res.end(),oneOfRes)==res.end())
                        res.push_back(oneOfRes);
                }
            }
            oneOfRes = tmpOneOfRes;
        }
    }
    vector<string> restoreIpAddresses(string s) {
        vector<string> res;
        string oneOfRes ;
        dfs(s,s.size(),0,res,oneOfRes,0);
        return res;
    }
};