CareerCup

private static final Pattern PATTERN = Pattern.compile(
"^(([01]?\\d\\d?|2[0-4]\\d|25[0-5])\\.){3}([01]?\\d\\d?|2[0-4]\\d|25[0-5])$");

public static boolean validate(final String ip) {
return PATTERN.matcher(ip).matches();
}

#include <iostream>
#include <vector>
#include <string>
#include <sstream>
#include <algorithm>
#include <iterator>

using namespace std;

// You won't need this
typedef char TCHAR;

vector<string> split(TCHAR* str, TCHAR delimiter)
{
const string data(str);
vector<string> elements;

string element;
for(int i = 0; i < data.size(); ++i)
{
if (data[i] == delimiter)
{
elements.push_back(element);
element.clear();
}
else
element += data[i];
}
elements.push_back(element);
return elements;
}

bool toInt(const string& str, int* result)
{
if (str.find_first_not_of("0123456789") != string::npos)
return false;

stringstream stream(str);
stream >> *result; // Should probably check the return value here
return true;
}

bool validate(TCHAR* ip)
{
const static TCHAR delimiter = '.';
const vector<string> parts = split(ip, delimiter);
if (parts.size() != 4)
return false;

for(int i = 0; i < parts.size(); ++i)
{
int part;
if (!toInt(parts[i], &part))
return false;
if (part < 0 || part > 255)
return false;
}
return true;
}

int main()
{
cout << validate("13.23.12.221") << endl;
return 0;
}

#include <iostream>
#include <vector>
#include <string>
#include <sstream>
#include <algorithm>
#include <iterator>

using namespace std;

// You won't need this
typedef char TCHAR;

vector<string> split(TCHAR* str, TCHAR delimiter)
{
const string data(str);
vector<string> elements;

string element;
for(int i = 0; i < data.size(); ++i)
{
if (data[i] == delimiter)
{
elements.push_back(element);
element.clear();
}
else
element += data[i];
}
elements.push_back(element);
return elements;
}

bool toInt(const string& str, int* result)
{
if (str.find_first_not_of("0123456789") != string::npos)
return false;

stringstream stream(str);
stream >> *result; // Should probably check the return value here
return true;
}

bool validate(TCHAR* ip)
{
const static TCHAR delimiter = '.';
const vector<string> parts = split(ip, delimiter);
if (parts.size() != 4)
return false;

for(int i = 0; i < parts.size(); ++i)
{
int part;
if (!toInt(parts[i], &part))
return false;
if (part < 0 || part > 255)
return false;
}
return true;
}

int main()
{
cout << validate("13.23.12.221") << endl;
return 0;
}

I am sure you are not looking for the answer. Simple answer would be to use a Regex or split based on . and compare each number.

Two implementations in C#

public static Boolean Validate(String ipAddress)
{
	String[] parts = ipAddress.Split('.');
	if (parts.Length != 4) return false;

	foreach(String s in parts)
	{
		Byte part;
		Boolean valid = Byte.TryParse(s, out part);
		if (valid == false) return false;
	}
	return true;
}

public static Boolean Validate2(String ipAddress)
{
	if (ipAddress == null) return false;
	Int32 partInt = 0;
	Int32 partCount = 0;

	for (int i = 0; i < ipAddress.Length; i++)
	{
		byte b = (Byte) (ipAddress[i] - '0');
		if ( b >= 0 && b <= 9)
		{
			partInt = partInt * 10 + b;
			if (partInt > 255)
			{
				return false;
			}
		}
		else if (ipAddress[i] == '.')
		{
			if ((partCount > 3) //only three allowed
				|| (i == 0)) //cannot be the first character
			{
				return false;
			}
			partCount++;
			partInt = 0;
		}
		else //any other character
		{
			return false;
		}
	}
	return true;
}