LeetCode Restore IP Addresses

Posted 2020-06-23 我本善良

DFS

 

class Solution {
public:
	vector<string> restoreIpAddresses(string s)
	{
		return insertDot(s, 0, 3);
	}
	
	vector<string> insertDot(string s, int beginIndex, int countOfDot /*3, 2, 1, 0*/)
	{
		vector<string> result;
		if( (s.size() - beginIndex) < (countOfDot + 1) || (s.size() - beginIndex - 1) > (countOfDot +1) * 3)
			return result;
		
		if(countOfDot == 0)
		{
			string partition = s.substr(beginIndex);
			if(partition.size() > 1 && partition[0] == ‘0‘) //Error 4: if the first char is 0, then no more chars, such as 1.00.1.1 is no valid;
			{
				return result;
			}
			int val = std::stoi(partition);
			if(val >= 0 && val <256)
			{
				result.push_back(partition);
			}
			return result;
		}
		
		for(int i = beginIndex + 1; i< s.size();i++ ) //Error 1: i< s.size() -1
		{
			string partition = s.substr(beginIndex, i - beginIndex);
			if(partition.size() > 1 && partition[0] == ‘0‘) //Error 3: if the first char is 0, then no more chars, such as 1.00.1.1 is no valid;
			{
				break;
			}
			int val = std::stoi(partition);
			if(val > 255)
				break;
			if(val >= 0 && val <256)
			{
				vector<string> subresult = insertDot(s, i, countOfDot - 1);
				if(subresult.size() != 0)
				{
					for(int j = 0; j< subresult.size(); j++) //Error 2: j< s.size() -1
					{
						string onepartition = partition + "." + subresult[j];
						result.push_back(onepartition);
					}
				}
			}
		}
		return result;
	}
};