TheAlgorithms-C-Plus-Plus/Sorting/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;
}