Find smallest permutation of given number

Difficulty Level : Easy
Last Updated : 04 May, 2021

Given a long integer, return the smallest(magnitude) integer permutation of that number.
Examples:

Input : 5468001
Output : 1004568

Input : 5341
Output : 1345

Question Source : GE digital Interview Experience | Set 6
We have already discussed a solution in below post.
Smallest number by rearranging digits of a given number
In this post, a different approach is discussed.
Approach : As number is long, store the number as string, sort the string, if there is no leading zero, return this string, if there is any leading zero, swap first element of string with first non-zero element of string, and return the string.
Below is the implementation of above approach :

C++

// CPP program to find smallest
// permutation of given number
#include <bits/stdc++.h>
using namespace std;
 
// return the smallest number permutation
string findSmallestPermutation(string s)
{
    int len = s.length();
 
    // sort the string
    sort(s.begin(), s.end());
 
    // check for leading zero in string
    // if there are any leading zeroes,
    // swap the first zero with first non-zero number
    int i = 0;
    while (s[i] == '0')
        i++;
     
    swap(s[0], s[i]);
    return s;
}
 
// driver program
int main()
{
    // take number input in string
    string s = "5468001";
    string res = findSmallestPermutation(s);
    cout << res << endl;
    return 0;
}

Java

// Java program to find smallest
// permutation of given number
import java.util.Arrays;
 
public class GFG {
     
    // return the smallest number permutation
    static char[] findSmallestPermutation(String s1)
    {
        // sort the string
        char s[] = s1.toCharArray();
        Arrays.sort(s);
      
        // check for leading zero in string
        // if there are any leading zeroes,
        // swap the first zero with first non-zero
        // number
        int i = 0;
        while (s[i] == '0')
            i++;
          
        char temp = s[0];
        s[0] = s[i];
        s[i] = temp;
        return s;
    }
      
    // driver program
    public static void main(String args[])
    {
        // take number input in string
        String s = "5468001";
        char res[] = findSmallestPermutation(s);
        System.out.println(res);
    }
}
// This code is contributed by Sumit Ghosh

Python

# Python program to find smallest
# permutation of given number
 
# Sort function
def sort_string(a):
    return ''.join(sorted(a))
 
# return the smallest number permutation
def findSmallestPermutation(s):
  
    # sort the string
    s = sort_string(s)
  
    # check for leading zero in string
    # if there are any leading zeroes,
    # swap the first zero with first non-zero number
    i = 0
    while (s[i] == '0'):
        i += 1
    a = list(s)
    temp = a[0]
    a[0] = a[i]
    a[i] = temp
    s = "".join(a)
    return s
  
# driver program
 
# take number input in string
s = "5468001"
res = findSmallestPermutation(s)
print res
 
# This code is contributed by Sachin Bisht

C#

// C# program to find smallest
// permutation of given number
using System;
 
public class GFG {
     
    // return the smallest number permutation
    static char[] findSmallestPermutation(string s1)
    {
         
        // sort the string
        char []s = s1.ToCharArray();;
        Array.Sort(s);
     
        // check for leading zero in string
        // if there are any leading zeroes,
        // swap the first zero with first non-zero
        // number
        int i = 0;
        while (s[i] == '0')
            i++;
         
        char temp = s[0];
        s[0] = s[i];
        s[i] = temp;
        return s;
    }
     
    // driver program
    public static void Main()
    {
         
        // take number input in string
        string s = "5468001";
         
        char []res = findSmallestPermutation(s);
        Console.WriteLine(res);
    }
}
 
// This code is contributed by vt_m.

PHP

<?php
// PHP program to find smallest
// permutation of given number
 
// return the smallest
// number permutation
function findSmallestPermutation($s)
{
    $len = strlen($s);
    $s = str_split($s);
     
    // sort the string
    sort($s);
 
    // check for leading zero
    // in string if there are
    // any leading zeroes,
    // swap the first zero with
    // first non-zero number
    $i = 0;
    while ($s[$i] == '0')
        $i++;
     
    $tmp = $s[0];
    $s[0] = $s[$i];
    $s[$i] = $tmp;
    $s=implode("", $s);
    return $s;
}
 
// Driver Code
 
// take number
// input in string
$s = "5468001";
$res = findSmallestPermutation($s);
echo $res;
 
// This code is contributed
// by mits.
?>

Javascript

// Javascript program to find smallest
// permutation of given number
 
// return the smallest
// number permutation
function findSmallestPermutation(s)
{
    let len = s.length;
    s = s.split("");
     
    // sort the string
    s = s.sort();
 
    // check for leading zero
    // in string if there are
    // any leading zeroes,
    // swap the first zero with
    // first non-zero number
    let i = 0;
    while (s[i] == '0')
        i++;
     
    let tmp = s[0];
    s[0] = s[i];
    s[i] = tmp;
    s=  s.join("");
    return s;
}
 
// Driver Code
 
// take number
// input in string
let s = "5468001";
let res = findSmallestPermutation(s);
document.write(res);
 
// This code is contributed
// by _saurabh_jaiswal

Output:

Optimization :
Since character set is limited (‘0’ to ‘9’), we can write our own sort method that works in linear time (by counting frequencies of all characters)
This article is contributed by Mandeep Singh. If you like GeeksforGeeks and would like to contribute, you can also write an article using write.geeksforgeeks.org or mail your article to contribute@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.
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