Find smallest permutation of given number in C++

In this problem, we are given a large number N. Our task is to find the smallest permutation of a given number.

Let’s take an example to understand the problem,

Input

N = 4529016

Output

1024569

Solution Approach

A simple solution to the problem is by storing the long integer value to a string. Then we will sort the string which is our result. But if there are any leading zeros, we will shift them after the first non zero value.

Program to illustrate the working of our solution,

Example

 Live Demo

#include <bits/stdc++.h>
using namespace std;
string smallestNumPer(string s) {
   int len = s.length();
   sort(s.begin(), s.end());
   int i = 0;
   while (s[i] == '0')
      i++;
   swap(s[0], s[i]);
   return s;
}
int main() {
   string s = "4529016";
   cout<<"The number is "<<s<<endl;
   cout<<"The smallest permutation of the number is "<<smallestNumPer(s);
   return 0;
}

Output

The number is 4529016
The smallest permutation of the number is 1024569