Restore IP Addresses

来源：互联网发布：java super.m = 10 编辑：程序博客网时间：2024/06/18 14:21

-----QUESTION-----

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)

-----SOLUTION-----

class Solution {public:    vector<string> restoreIpAddresses(string s) {        result.clear();        dfs(s, 0, 0);        return result;    }    void dfs(string s, int startPos, int depth)    {        if (depth ==3)        {            string str = s.substr(startPos,s.length()-startPos);            int restStrLen = str.length();            int n = atoi(str.c_str());            if(n>255) return;            if(restStrLen > 1 && s[startPos]=='0') return;            result.push_back(s);        }        else        {                   string str = s.substr(startPos,s.length()-startPos);            int restStrLen = str.length();            if(restStrLen>=4-depth)            {                         str = s.substr(0,startPos+1)+"."+s.substr(startPos+1,restStrLen-1);                dfs(str, startPos+2, depth+1);                 if(s[startPos] == '0') return;            }            if(restStrLen>=5-depth)            {                str = s.substr(0,startPos+2) +"."+s.substr(startPos+2,restStrLen-2);                dfs(str, startPos+3, depth+1);            }            if(restStrLen>=6-depth)            {                str =  s.substr(startPos,3);                int n = atoi(str.c_str());                if(n>255) return;                str = s.substr(0,startPos+3)+"."+s.substr(startPos+3,restStrLen-3);                dfs(str, startPos+4, depth+1);            }        }    }private:    vector<string> result;};

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