Rearrange Odd and Even values in Alternate Fashion in Ascending Order

Given an array of integers (both odd and even), the task is to arrange them in such a way that odd and even values come in alternate fashion in non-decreasing order(ascending) respectively.

  • If the smallest value is Even then we have to print Even-Odd pattern.
  • If the smallest value is Odd then we have to print Odd-Even pattern.

Note: No. of odd elements must be equal to No. of even elements in the input array.

Examples:



Input: arr[] = {1, 3, 2, 5, 4, 7, 10}
Output: 1, 2, 3, 4, 5, 10, 7
Smallest value is 1(Odd) so output will be Odd-Even pattern.

Input: arr[] = {9, 8, 13, 2, 19, 14}
Output: 2, 9, 8, 13, 14, 19
Smallest value is 2(Even) so output will be Even-Odd pattern.

Asked In: Microsoft Tech-Set-Go-2018

Algorithm:

  1. Sort the given array.
  2. Insert Even values in List-1 and Odd values in List-2.
  3. Now if the smallest value is even, then insert an even value from list 1 and odd value from list 2 to original array and so on.
  4. But if the smallest value is odd, then insert an odd value from list 2 and even value from list 1 to original array and so on.

Below is the implementation of the above approach:

C++

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// C++ implementation of the above approach
#include <bits/stdc++.h>
using namespace std;
  
void AlternateRearrange(int arr[], int n)
{
    // Sort the array
    sort(arr, arr + n);
  
    vector<int> v1; // to insert even values
    vector<int> v2; // to insert odd values
  
    for (int i = 0; i < n; i++)
        if (arr[i] % 2 == 0)
            v1.push_back(arr[i]);
        else
            v2.push_back(arr[i]);
  
    int index = 0, i = 0, j = 0;
  
    bool flag = false;
  
    // Set flag to true if first element is even
    if (arr[0] % 2 == 0)
        flag = true;
  
    // Start rearranging array
    while (index < n) {
  
        // If first element is even
        if (flag == true) {
            arr[index++] = v1[i++];
            flag = !flag;
        }
  
        // Else, first element is Odd
        else {
            arr[index++] = v2[j++];
            flag = !flag;
        }
    }
  
    // Print the rearranged array
    for (i = 0; i < n; i++)
        cout << arr[i] << " ";
}
  
// Driver code
int main()
{
    int arr[] = { 9, 8, 13, 2, 19, 14 };
    int n = sizeof(arr) / sizeof(int);
    AlternateRearrange(arr, n);
    return 0;
}

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Java














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// Java implementation of the above approach  


  


import java.util.* ; 


  


class GFG 


{ 


  


    static void AlternateRearrange(int arr[], int n)  


    {  


        // Sort the array 


          


        // Collection.sort() sorts the 


        // collection in ascending order 


        Arrays.sort(arr) ; 


          


        Vector v1 = new Vector(); // to insert even values  


        Vector v2 = new Vector(); // to insert odd values  


      


        for (int i = 0; i < n; i++)  


            if (arr[i] % 2 == 0)  


                v1.add(arr[i]);  


            else


                v2.add(arr[i]);  


      


        int index = 0, i = 0, j = 0;  


      


        boolean flag = false;  


      


        // Set flag to true if first element is even  


        if (arr[0] % 2 == 0)  


            flag = true;  


      


        // Start rearranging array  


        while (index < n)  


        {  


      


            // If first element is even  


            if (flag == true)  


            {  


                arr[index] = (int)v1.get(i);  


                i += 1 ; 


                index += 1 ; 


                flag = !flag;  


            }  


      


            // Else, first element is Odd  


            else


            {  


                arr[index] = (int)v2.get(j) ;  


                j += 1 ; 


                index += 1 ; 


                flag = !flag;  


            }  


        }  


      


        // Print the rearranged array  


        for (i = 0; i < n; i++)  


            System.out.print(arr[i] + " ");  


    }  


      


    // Driver code  


    public static void main(String []args)  


    {  


        int arr[] = { 9, 8, 13, 2, 19, 14 };  


        int n = arr.length ; 


      


        AlternateRearrange(arr, n);  


    }  


} 


  


// This code is contributed by aishwarya.27 



















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Python3














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# Python3 implementation of the above approach 


  


def AlternateRearrange(arr, n): 


  


    # Sort the array 


    arr.sort() 


  


    v1 = list() # to insert even values 


    v2 = list() # to insert odd values 


  


    for i in range(n): 


        if (arr[i] % 2 == 0): 


            v1.append(arr[i]) 


        else: 


            v2.append(arr[i]) 


  


    index = 0


    i = 0


    j = 0


  


    flag = False


  


    # Set flag to true if first element is even 


    if (arr[0] % 2 == 0): 


        flag = True


  


    # Start rearranging array 


    while (index < n):  


  


        # If first element is even 


        if (flag == True): 


            arr[index] = v1[i] 


            index += 1


            i += 1


            flag = ~flag 


          


        # Else, first element is Odd 


        else: 


            arr[index] = v2[j] 


            index += 1


            j += 1


  


            flag = ~flag 


          


    # Print the rearranged array 


    for i in range(n): 


        print(arr[i], end = " ") 


  


# Driver code 


arr = [ 9, 8, 13, 2, 19, 14]  


n = len(arr) 


  


AlternateRearrange(arr, n) 


  


# This code is contributed  


# by Mohit Kumar 29 



















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C#














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// C# implementation of the above approach  


  


using System; 


using System.Collections; 


class GFG 


{ 


  


    static void AlternateRearrange(int []arr, int n)  


    {  


        // Sort the array 


          


        // Collection.sort() sorts the 


        // collection in ascending order 


        Array.Sort(arr) ; 


          


        ArrayList v1 = new ArrayList(); // to insert even values  


        ArrayList v2 = new ArrayList(); // to insert odd values  


      


        for (int j = 0; j < n; j++)  


            if (arr[j] % 2 == 0)  


                v1.Add(arr[j]);  


            else


                v2.Add(arr[j]);  


      


        int index = 0, i = 0, k = 0;  


      


        bool flag = false;  


      


        // Set flag to true if first element is even  


        if (arr[0] % 2 == 0)  


            flag = true;  


      


        // Start rearranging array  


        while (index < n)  


        {  


      


            // If first element is even  


            if (flag == true)  


            {  


                arr[index] = (int)v1[i];  


                i += 1 ; 


                index += 1 ; 


                flag = !flag;  


            }  


      


            // Else, first element is Odd  


            else


            {  


                arr[index] = (int)v2[k] ;  


                k += 1 ; 


                index += 1 ; 


                flag = !flag;  


            }  


        }  


      


        // Print the rearranged array  


        for (i = 0; i < n; i++)  


            Console.Write(arr[i] + " ");  


    }  


      


    // Driver code  


    static void Main()  


    {  


        int []arr = { 9, 8, 13, 2, 19, 14 };  


        int n = arr.Length ; 


      


        AlternateRearrange(arr, n);  


    }  


} 


  


// This code is contributed by mits 



















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PHP














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<?php 


// PHP implementation of the above approach  


function AlternateRearrange($arr, $n) 


{ 


  


    // Sort the array 


    sort($arr);  


  


    $v1 = array(); // to insert even values  


    $v2 = array(); // to insert odd values  


  


    for ($i = 0; $i < $n; $i++)  


        if ($arr[$i] % 2 == 0)  


            array_push($v1, $arr[$i]);  


        else


            array_push($v2, $arr[$i]);  


  


    $index = 0; 


    $i = 0; 


    $j = 0; 


  


    $flag = false;  


  


    // Set flag to true if first element is even  


    if ($arr[0] % 2 == 0)  


        $flag = true;  


  


    // Start rearranging array  


    while ($index < $n)  


    {  


  


        // If first element is even  


        if ($flag == true)  


        {  


            $arr[$index++] = $v1[$i++];  


            $flag = !$flag;  


        }  


  


        // Else, first element is Odd  


        else 


        {  


            $arr[$index++] = $v2[$j++];  


            $flag = !$flag;  


        }  


    }  


  


    // Print the rearranged array  


    for ($i = 0; $i < $n; $i++)  


        echo $arr[$i], " " ;  


}  


  


// Driver code  


$arr = array( 9, 8, 13, 2, 19, 14 ); 


$n = sizeof($arr); 


  


AlternateRearrange($arr, $n);  


  


// This code is contributed by Ryuga 


?> 



















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Output:


2 9 8 13 14 19







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