Program in C++ to convert string to number.

sn.cpp

// Author: Amit Kumar Jaiswal
// Twitter: @amit_gkp

#include<iostream>
#include<string>
#include<cstdlib>
using namespace std;

long hex2int(const string& hexStr)
{
	char *offset;
	if(hexStr.length()>2)
	{
		if(hexStr[0]=='0' && hexStr[1]=='x')
		{
			return strtol(hexStr.c_str(),&offset,0);
		}
	}
	return strtol(hexStr.c_str(),&offset,16);
}
int main()
{
	string str1="0x12AB";
	cout<<hex2int(str1)<<endl;
	string str2="12AB";
	cout<<hex2int(str2)<<endl;
	string str3="QAFG";
	cout<<hex2int(str3)<<endl;
}