Smallest number by rearranging digits of a given number

Find the Smallest number (Not leading Zeros) which can be obtained by rearranging the digits of given number.

Examples:

Input: n = 846903
Output: 304689

Input: n = 55010
Output: 10055

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

Steps to find the smallest number.

Count the frequency of each digit in the number.
Place the smallest digit (except 0) at the left most of required number.
and decrement the frequency of that digit by 1.
Place all remaining digits in ascending order from left to right.

This solution is based on counting sort.

C++

// C++ program for finding smallest number 
// from digits of given number 
#include<iostream> 
using namespace std; 
  
// function to find the smallest number 
int smallest(int num) 
{ 
    // initialize frequency of each digit to Zero 
    int freq[10] = {0}; 
  
    // count frequency of each digit in the number 
    while (num) 
    { 
        int d = num % 10; // extract last digit 
        freq[d]++; // increment counting 
        num = num / 10; //remove last digit 
    } 
  
    // Set the LEFTMOST digit to minimum expect 0 
    int result = 0; 
    for (int i = 1 ; i <= 9 ; i++) 
    { 
        if (freq[i]) 
        { 
            result = i; 
            freq[i]--; 
            break; 
        } 
    } 
  
    // arrange all remaining digits 
    // in ascending order 
    for (int i = 0 ; i <= 9 ; i++) 
        while (freq[i]--) 
            result = result * 10 + i; 
  
    return result; 
} 
  
// Driver Program 
int main() 
{ 
    int num = 570107; 
    cout << smallest(num); 
    return 0; 
} 

Java

// Java program for finding smallest number 
// from digits of given number 
public class GFG { 
  
    // function to find the smallest number 
    static int smallest(int num) 
    { 
        // initialize frequency of each digit to Zero 
        int[] freq = new int[10]; 
       
        // count frequency of each digit in the number 
        while (num > 0) 
        { 
            int d = num % 10; // extract last digit 
            freq[d]++; // increment counting 
            num = num / 10; //remove last digit 
        } 
       
        // Set the LEFTMOST digit to minimum expect 0 
        int result = 0; 
        for (int i = 1 ; i <= 9 ; i++) 
        { 
            if (freq[i] != 0) 
            { 
                result = i; 
                freq[i]--; 
                break; 
            } 
        } 
       
        // arrange all remaining digits 
        // in ascending order 
        for (int i = 0 ; i <= 9 ; i++) 
            while (freq[i]-- != 0) 
                result = result * 10 + i; 
       
        return result; 
    } 
       
    // Driver Program 
    public static void main(String args[]) 
    { 
        int num = 570107; 
        System.out.println(smallest(num)); 
    } 
} 
// This code is contributed by Sumit Ghosh 

Python

# Function to find the smallest number 
def smallest(lst): 
      
    # Here i is index and n is the number of the list 
    for i,n in enumerate(lst):  
          
        # Checking for the first non-zero digit in the sorted list 
        if n != '0':  
              
            # Remove and store the digit from the lst 
            tmp = lst.pop(i) 
            break
      
    # Place the first non-zero digit at the starting 
    # and return the final number 
    return str(tmp) + ''.join(lst)  
  
  
# Driver program 
if __name__ == '__main__': 
      
    # Converting the given numbers into string to form a list 
    lst = list(str(570107)) 
    lst.sort() 
      
    # Calling the function using the above list 
    print smallest(lst) 
      
# This code is contributed by Mahendra Yadav 

C#

// C# program for finding smallest 
// number from digits of given  
// number 
using System; 
  
public class GFG { 
  
    // function to find the smallest 
    // number 
    static int smallest(int num) 
    { 
          
        // initialize frequency of  
        // each digit to Zero 
        int[] freq = new int[10]; 
      
        // count frequency of each  
        // digit in the number 
        while (num > 0) 
        { 
              
            // extract last digit 
            int d = num % 10; 
              
            // increment counting 
            freq[d]++; 
              
            //remove last digit 
            num = num / 10; 
        } 
      
        // Set the LEFTMOST digit to  
        // minimum expect 0 
        int result = 0; 
        for (int i = 1 ; i <= 9 ; i++) 
        { 
            if (freq[i] != 0) 
            { 
                result = i; 
                freq[i]--; 
                break; 
            } 
        } 
      
        // arrange all remaining digits 
        // in ascending order 
        for (int i = 0 ; i <= 9 ; i++) 
            while (freq[i]-- != 0) 
                result = result * 10 + i; 
      
        return result; 
    } 
      
    // Driver Program 
    public static void Main() 
    { 
        int num = 570107; 
        Console.WriteLine(smallest(num)); 
    } 
} 
  
// This code is contributed by anuj_67. 

PHP

<?php 
// PHP program for finding smallest  
// number from digits of given number 
  
// function to find the smallest number 
function smallest($num) 
{ 
    // initialize frequency of  
    // each digit to Zero 
    $freq = array_fill(0, 10, 0); 
  
    // count frequency of each  
    // digit in the number 
    while ($num) 
    { 
        $d = $num % 10; // extract last digit 
        $freq[$d]++; // increment counting 
        $num = (int)($num / 10); // remove last digit 
    } 
  
    // Set the LEFTMOST digit 
    // to minimum expect 0 
    $result = 0; 
    for ($i = 1 ; $i <= 9 ; $i++) 
    { 
        if ($freq[$i]) 
        { 
            $result = $i; 
            $freq[$i]--; 
            break; 
        } 
    } 
  
    // arrange all remaining digits 
    // in ascending order 
    for ($i = 0 ; $i <= 9 ; $i++) 
        while ($freq[$i] > 0) 
        { 
            $result = $result * 10 + $i; 
            $freq[$i] -= 1; 
        } 
  
    return $result; 
} 
  
// Driver Code 
$num = 570107; 
echo smallest($num); 
  
// This code is contributed by mits 
?> 

Output:

Another Approach:Find smallest permutation of given number

This article is contributed by Ajay Kumar Agrahari(aJy aGr). 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.

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My Personal Notes

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

C++

Java

Python

C#

PHP

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