NumericStringSort.cpp

//Using general algorithms to sort a collection of strings results in alphanumeric sort.
//If it is a numeric string, it leads to unnatural sorting

//eg, an array of strings 1,10,100,2,20,200,3,30,300
//would be sorted in that same order by using conventional sorting,
//even though we know the correct sorting order is 1,2,3,10,20,30,100,200,300

//This Programme uses a comparator to sort the array in Numerical order instead of Alphanumeric order


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

bool NumericSort(string a,string b)
{
  while(a[0]=='0')
  {
    a.erase(a.begin());
  }
  while(b[0]=='0')
  {
    b.erase(b.begin());
  }  
    int n=a.length();
    int m=b.length();
  if(n==m)
    return a<b;
  return n<m;
}

int main()
{

int n;
cout << "Enter number of elements to be sorted Numerically\n";
cin >> n;

vector<string> v(n);
cout << "Enter the string of Numbers\n";
for(int i=0;i<n;i++)
{
cin >> v[i];
}

sort(v.begin(),v.end());
cout << "Elements sorted normally \n";
for(int i=0;i<n;i++)
{
cout << v[i] << " ";
}
cout << "\n";

sort(v.begin(),v.end(),NumericSort);
cout << "Elements sorted Numerically \n";
for(int i=0;i<n;i++)
{
cout << v[i] << " ";
}


return 0;
}