【算法刷题】leetcode 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)

 

class Solution {
public:
	bool isIP(string str)
	{
        //若数字位数大于1，首位不能为0
        if (str.length()>1 && str[0] == '0')
		{
			return false;
		}
		int temp = stoi(str);
		return (temp >= 0) && (temp <= 255);
	}
	void DFS(vector& result,string& s, string& temp, int count, int pos, int length)
	{
		if (count == 4 && pos == length)
		{
            //删除最后一个'.'
            temp = temp.erase(length+3,1);
			result.push_back(temp);
			return;
		}
        
		for (int i=1;i<=3 && pos+i<=length;++i)
		{
			string num = s.substr(pos, i);
			if (isIP(num))
			{
                string temp1= temp;
				temp += num;
				temp += '.';
				DFS(result, s, temp, count + 1, pos + i, length);
                //回溯还原
                temp = temp1;

			}
		}
	
	}


	vector restoreIpAddresses(string s) {
		int len = s.length();
		vector res;
		if (len < 4 || len>12)
			return res;

		string itemp;
		DFS(res,s, itemp, 0, 0, len);
		return res;
	}
};