Find smallest permutation of given number

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

Examples:

Input : 5468001
Output : 1004568

Input : 5341
Output : 1345

Recommended: Please solve it on “PRACTICE ” first, before moving on to the solution.

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. 
?> 

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 contribute.geeksforgeeks.org or mail your article to contribute@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.

Please write comments if you find anything incorrect, or you want to share more information about the topic discussed above.

Attention reader! Don’t stop learning now. Get hold of all the important DSA concepts with the DSA Self Paced Course at a student-friendly price and become industry ready.

My Personal Notes

Recommended: Please solve it on “PRACTICE ” first, before moving on to the solution.

C++

Java

Python

C#

PHP

Recommended Posts: