Valid_number

// This is a C++ code which determines whether a number is valid or not...

// If a number starts with 0 then it should be of size 11 with every element be a digit from 0 to 9 else it should be of size 10 with every element be a digit from 0 to 9...

#include<bits/stdc++.h> 
using namespace std; 

int main()
{
	cout << "Enter the number : ";
	string s;
	cin >> s;
	if(s.length()==10 || s.length()==11 && s[0]=='0')
	{
		for(int i=0;i<s.length();i++)
		{
			if((s[i]-'0')<0 && (s[i]-'0')>9)
			{
				cout << "Not a valid number..."; 
				break;
			}
		}
		cout << "It's a valid number...";
	}
	else
		cout << "Not a valid number...";
}