Sort all even numbers in ascending order and then sort all odd numbers in descending order
Given an array of integers (both odd and even), sort them in such a way that the first part of the array contains odd numbers sorted in descending order, rest portion contains even numbers sorted in ascending order.
Examples:
Input : arr[] = {1, 2, 3, 5, 4, 7, 10} Output : arr[] = {7, 5, 3, 1, 2, 4, 10} Input : arr[] = {0, 4, 5, 3, 7, 2, 1} Output : arr[] = {7, 5, 3, 1, 0, 2, 4}
Method 1 (Using Partition)
- Partition the input array such that all odd elements are moved to left and all even elements on right. This step takes O(n).
- Once the array is partitioned, sort left and right parts individually. This step takes O(n Log n).
Below is the implementation of the above idea.
C++
// C++ program sort array in even and odd manner. // The odd numbers are to be sorted in descending // order and the even numbers in ascending order #include <bits/stdc++.h> using namespace std; // To do two way sort. First sort even numbers in // ascending order, then odd numbers in descending // order. void twoWaySort( int arr[], int n) { // Current indexes from left and right int l = 0, r = n - 1; // Count of odd numbers int k = 0; while (l < r) { // Find first even number // from left side. while (arr[l] % 2 != 0) { l++; k++; } // Find first odd number // from right side. while (arr[r] % 2 == 0 && l < r) r--; // Swap even number present on left and odd // number right. if (l < r) swap(arr[l], arr[r]); } // Sort odd number in descending order sort(arr, arr + k, greater< int >()); // Sort even number in ascending order sort(arr + k, arr + n); } // Driver code int main() { int arr[] = { 1, 3, 2, 7, 5, 4 }; int n = sizeof (arr) / sizeof ( int ); twoWaySort(arr, n); for ( int i = 0; i < n; i++) cout << arr[i] << " " ; return 0; } |
Java
// Java program sort array in even and odd manner. // The odd numbers are to be sorted in descending // order and the even numbers in ascending order import java.util.Arrays; import java.util.Collections; public class GFG { // To do two way sort. First sort even numbers in // ascending order, then odd numbers in descending // order. static void twoWaySort(Integer arr[], int n) { // Current indexes from left and right int l = 0 , r = n - 1 ; // Count of odd numbers int k = 0 ; while (l < r) { // Find first even number from left side. while (arr[l] % 2 != 0 ) { l++; k++; } // Find first odd number from right side. while (arr[r] % 2 == 0 && l < r) r--; // Swap even number present on left and odd // number right. if (l < r) { // swap arr[l] arr[r] int temp = arr[l]; arr[l] = arr[r]; arr[r] = temp; } } // Sort odd number in descending order Arrays.sort(arr, 0 , k, Collections. reverseOrder()); // Sort even number in ascending order Arrays.sort(arr, k, n); } // Driver Method public static void main(String[] args) { Integer arr[] = { 1 , 3 , 2 , 7 , 5 , 4 }; twoWaySort(arr, arr.length); System.out.println(Arrays.toString(arr)); } } |
Python
# Python program to sort array # in even and odd manner # The odd numbers are to be # sorted in descending order # and the even numbers in # ascending order # To do two way sort. First # sort even numbers in ascending # order, then odd numbers in # descending order. def two_way_sort(arr, arr_len): # Current indexes l->left # and r->right l, r = 0 , arr_len - 1 # Count of number of # odd numbers, used in # slicing the array later. k = 0 # Run till left(l) < right(r) while (l < r): # While left(l) is odd, if yes # increment the left(l) plus # odd count(k) if not break the # while for even number found # here to be swapped while (arr[l] % 2 ! = 0 ): l + = 1 k + = 1 # While right(r) is even, # if yes decrement right(r) # if not break the while for # odd number found here to # be swapped while (arr[r] % 2 = = 0 and l < r): r - = 1 # Swap the left(l) and right(r), # which is even and odd numbers # encountered in above loops if (l < r): arr[l], arr[r] = arr[r], arr[l] # Slice the number on the # basis of odd count(k) odd = arr[:k] even = arr[k:] # Sort the odd and # even array accordingly odd.sort(reverse = True ) even.sort() # Extend the odd array with # even values and return it. odd.extend(even) return odd # Driver code arr_len = 6 arr = [ 1 , 3 , 2 , 7 , 5 , 4 ] result = two_way_sort(arr, arr_len) for i in result: print ( str (i) + " " ), # This code is contributed # by JaySiyaRam |
C#
// C# program sort array in even and odd manner. // The odd numbers are to be sorted in descending // order and the even numbers in ascending order using System; using System.Linq; class GFG { // To do two way sort. First sort even numbers in // ascending order, then odd numbers in descending // order. static void twoWaySort( int [] arr, int n) { // Current indexes from left and right int l = 0, r = n - 1; // Count of odd numbers int k = 0; while (l < r) { // Find first even number // from left side. while (arr[l] % 2 != 0) { l++; k++; } // Find first odd number from right side. while (arr[r] % 2 == 0 && l < r) r--; // Swap even number present // on left and odd // number right. if (l < r) { // swap arr[l] arr[r] int temp = arr[l]; arr[l] = arr[r]; arr[r] = temp; } } // Sort odd number in descending order Array.Sort(arr, 0, k); Array.Reverse(arr, 0, k); // Sort even number in ascending order Array.Sort(arr, k, n - k); } // Driver Method public static void Main(String[] args) { int [] arr = { 1, 3, 2, 7, 5, 4 }; twoWaySort(arr, arr.Length); Console.WriteLine(String.Join( " " , arr)); } } // This code has been contributed by 29AjayKumar |
Javascript
<script> // Javascript program sort array // in even and odd manner. // The odd numbers are to be // sorted in descending // order and the even numbers in // ascending order // To do two way sort. // First sort even numbers in // ascending order, then odd // numbers in descending // order. function twoWaySort(arr,n) { // Current indexes from // left and right let l = 0, r = n - 1; // Count of odd numbers let k = 0; while (l < r) { // Find first even number // from left side. while (arr[l] % 2 != 0) { l++; k++; } // Find first odd number // from right side. while (arr[r] % 2 == 0 && l < r) r--; // Swap even number present // on left and odd // number right. if (l < r) { // swap arr[l] arr[r] let temp = arr[l]; arr[l] = arr[r]; arr[r] = temp; } } let odd= new Array(k); for (let i=0;i<k;i++) { odd[i]=arr[i]; } let even= new Array(n-k); for (let i=0;i<n-k;i++) { even[i]=arr[k+i]; } // Sort odd number in descending order odd.sort( function (a,b){ return b-a;}); // Sort even number in ascending order even.sort( function (a,b){ return a-b;}); return odd.concat(even); } // Driver Method let arr=[1, 3, 2, 7, 5, 4 ]; let ans=twoWaySort(arr, arr.length); for (let i=0;i<ans.length;i++) { document.write(ans[i]+ " " ); } // This code is contributed by rag2127 </script> |
Output:
7 5 3 1 2 4
Time complexity: O(n log n)
Space complexity: O(1)
Method 2 (Using negative multiplication) :
- Make all odd numbers negative.
- Sort all numbers.
- Revert the changes made in step 1 to get original elements back.
C++
// C++ program sort array in even and odd manner. // The odd numbers are to be sorted in descending // order and the even numbers in ascending order #include <bits/stdc++.h> using namespace std; // To do two way sort. First sort even numbers in // ascending order, then odd numbers in descending // order. void twoWaySort( int arr[], int n) { // Make all odd numbers negative for ( int i = 0; i < n; i++) if (arr[i] & 1) // Check for odd arr[i] *= -1; // Sort all numbers sort(arr, arr + n); // Retaining original array for ( int i = 0; i < n; i++) if (arr[i] & 1) arr[i] *= -1; } // Driver code int main() { int arr[] = { 1, 3, 2, 7, 5, 4 }; int n = sizeof (arr) / sizeof ( int ); twoWaySort(arr, n); for ( int i = 0; i < n; i++) cout << arr[i] << " " ; return 0; } |
Java
// Java program sort array in even and odd manner. // The odd numbers are to be sorted in descending // order and the even numbers in ascending order import java.util.Arrays; public class GFG { // To do two way sort. First sort even numbers in // ascending order, then odd numbers in descending // order. static void twoWaySort( int arr[], int n) { // Make all odd numbers negative for ( int i = 0 ; i < n; i++) if ((arr[i] & 1 ) != 0 ) // Check for odd arr[i] *= - 1 ; // Sort all numbers Arrays.sort(arr); // Retaining original array for ( int i = 0 ; i < n; i++) if ((arr[i] & 1 ) != 0 ) arr[i] *= - 1 ; } // Driver Method public static void main(String[] args) { int arr[] = { 1 , 3 , 2 , 7 , 5 , 4 }; twoWaySort(arr, arr.length); System.out.println(Arrays.toString(arr)); } } |
Python3
# Python 3 program to sort array in # even and odd manner. The odd # numkbers are to be sorted in # descending order and the even # numbers in ascending order # To do two way sort. First sort # even numbers in ascending order, # then odd numbers in descending order. def twoWaySort(arr, n): # Make all odd numbers negative for i in range ( 0 , n): # Check for odd if (arr[i] & 1 ): arr[i] * = - 1 # Sort all numbers arr.sort() # Retaining original array for i in range ( 0 , n): if (arr[i] & 1 ): arr[i] * = - 1 # Driver code arr = [ 1 , 3 , 2 , 7 , 5 , 4 ] n = len (arr) twoWaySort(arr, n); for i in range ( 0 , n): print (arr[i], end = " " ) # This code is contributed by Smitha Dinesh Semwal |
C#
// Java program sort array in even and // odd manner. The odd numbers are to // be sorted in descending order and // the even numbers in ascending order using System; public class GFG { // To do two way sort. First sort // even numbers in ascending order, // then odd numbers in descending // order. static void twoWaySort( int [] arr, int n) { // Make all odd numbers negative for ( int i = 0; i < n; i++) // Check for odd if ((arr[i] & 1) != 0) arr[i] *= -1; // Sort all numbers Array.Sort(arr); // Retaining original array for ( int i = 0; i < n; i++) if ((arr[i] & 1) != 0) arr[i] *= -1; } // Driver Method public static void Main() { int [] arr = { 1, 3, 2, 7, 5, 4 }; twoWaySort(arr, arr.Length); for ( int i = 0; i < arr.Length; i++) Console.Write(arr[i] + " " ); } } // This code is contributed by Smitha |
PHP
<?php // PHP program sort array in even and odd manner. // The odd numbers are to be sorted in descending // order and the even numbers in ascending order // To do two way sort. First sort even numbers in // ascending order, then odd numbers in descending // order. function twoWaySort(& $arr , $n ) { // Make all odd numbers negative for ( $i = 0 ; $i < $n ; $i ++) if ( $arr [ $i ] & 1) // Check for odd $arr [ $i ] *= -1; // Sort all numbers sort( $arr ); // Retaining original array for ( $i = 0 ; $i < $n ; $i ++) if ( $arr [ $i ] & 1) $arr [ $i ] *= -1; } // Driver code $arr = array (1, 3, 2, 7, 5, 4); $n = sizeof( $arr ); twoWaySort( $arr , $n ); for ( $i = 0; $i < $n ; $i ++) echo $arr [ $i ] . " " ; // This code is contributed by ita_c ?> |
Javascript
<script> // Javascript program sort array in even and odd manner. // The odd numbers are to be sorted in descending // order and the even numbers in ascending order // To do two way sort. First sort even numbers in // ascending order, then odd numbers in descending // order. function twoWaySort(arr, n) { // Make all odd numbers negative for (let i = 0; i < n; i++) if (arr[i] & 1) // Check for odd arr[i] *= -1; // Sort all numbers arr.sort((a,b) => a-b); // Retaining original array for (let i = 0; i < n; i++) if (arr[i] & 1) arr[i] *= -1; } // Driver code let arr = [ 1, 3, 2, 7, 5, 4 ]; let n = arr.length; twoWaySort(arr, n); for (let i = 0; i < n; i++) document.write(arr[i] + " " ); //This code is contributed by Mayank Tyagi </script> |
Output:
7 5 3 1 2 4
Time complexity: O(n log n)
Space complexity: O(1)
This method may not work when input array contains negative numbers. However, there is a way to handle this. We count the positive odd integers in the input array then sort again. Readers may refer this for implementation.
Method 3 (Using comparator):
This problem can be easily solved by using the inbuilt sort function with a custom compare method. On comparing any two elements there will be three cases:
- When both the elements are even: In this case, the smaller element must appear in the left of the larger element in the sorted array.
- When both the elements are odd: The larger element must appear on left of the smaller element.
- One is odd and the other is even: The element which is odd must appear on the left of the even element.
Below is the implementation of the above approach:
CPP
// C++ implementation of the approach #include <bits/stdc++.h> using namespace std; // Utility function to print // the contents of the array void printArr( int arr[], int n) { for ( int i = 0; i < n; i++) cout << arr[i] << " " ; } // To do two way sort. Make comparator function // for the inbuilt sort function of c++ such that // odd numbers are placed before even in descending // and ascending order respectively bool compare( int a, int b) { // If both numbers are even, // smaller number should // be placed at lower index if (a % 2 == 0 && b % 2 == 0) return a < b; // If both numbers are odd larger number // should be placed at lower index if (a % 2 != 0 && b % 2 != 0) return b < a; // If a is odd and b is even, // a should be placed before b if (a % 2 != 0) return true ; // If b is odd and a is even, // b should be placed before a return false ; } // Driver code int main() { int arr[] = { 1, 3, 2, 7, 5, 4 }; int n = sizeof (arr) / sizeof ( int ); // Sort the array sort(arr, arr + n, compare); // Print the sorted array printArr(arr, n); return 0; } // This code is contributed by Nikhil Yadav |
Java
// Java implementation of the approach import java.util.ArrayList; import java.util.Collections; import java.util.Comparator; class GFG { // Utility function to print // the contents of the array static void printArr(ArrayList<Integer> arr, int n) { for ( int i = 0 ; i < n; i++) System.out.print(arr.get(i) + " " ); } // Driver code public static void main(String args[]) { ArrayList<Integer> arr = new ArrayList<Integer>(); arr.add( 1 ); arr.add( 3 ); arr.add( 2 ); arr.add( 7 ); arr.add( 5 ); arr.add( 4 ); int n = arr.size(); // Sort the array Collections.sort(arr, new Comparator<Integer>() { @Override public int compare(Integer a, Integer b) { // If both numbers are even, // smaller number should // be placed at lower index if (a % 2 == 0 && b % 2 == 0 ) return (a - b); // If both numbers are odd larger number // should be placed at lower index if (a % 2 != 0 && b % 2 != 0 ) return (b - a); // If a is odd and b is even, // a should be placed before b if (a % 2 != 0 ) return 1 ; // If b is odd and a is even, // b should be placed before a return 0 ; } }); // Print the sorted array printArr(arr, n); } } // This code is contributed by Saurabh Jaiswal |
Python3
# Python3 implementation of the approach # Utility function to print # the contents of the array from functools import cmp_to_key def printArr(arr, n): for i in range (n): print (arr[i], end = " " ) # To do two way sort. Make comparator function # for the inbuilt sort function of c++ such that # odd numbers are placed before even in descending # and ascending order respectively def compare(a, b): # If both numbers are even, # smaller number should # be placed at lower index if (a % 2 = = 0 and b % 2 = = 0 and a < b): return - 1 # If both numbers are odd larger number # should be placed at lower index if (a % 2 ! = 0 and b % 2 ! = 0 and b > a): return 1 # If a is odd and b is even, # a should be placed before b if (a % 2 ! = 0 ): return - 1 # If b is odd and a is even, # b should be placed before a return 1 # Driver code arr = [ 1 , 3 , 2 , 7 , 5 , 4 ] n = len (arr) # Sort the array arr.sort(key = cmp_to_key(compare)) # Print the sorted array printArr(arr, n) # This code is contributed by shinjanpatra |
C#
// C# implementation of the approach using System; using System.Collections.Generic; public class GFG { // Utility function to print // the contents of the array static void printArr(List< int > arr, int n) { for ( int i = 0; i < n; i++) Console.Write(arr[i] + " " ); } private static int Compare( int a, int b) { // If both numbers are even, // smaller number should // be placed at lower index if (a % 2 == 0 && b % 2 == 0 && a<b) return -1; // If both numbers are odd larger number // should be placed at lower index if (a % 2 != 0 && b % 2 != 0 && b>a) return 1; // If a is odd and b is even, // a should be placed before b if (a % 2 != 0) return -1; // If b is odd and a is even, // b should be placed before a return 1; } // Driver code public static void Main(String []args) { List< int > arr = new List< int >(); arr.Add(1); arr.Add(3); arr.Add(2); arr.Add(7); arr.Add(5); arr.Add(4); int n = arr.Count; // Sort the array arr.Sort(Compare); // Print the sorted array printArr(arr, n); } } // This code is contributed by 29AjayKumar |
Javascript
<script> // JavaScript implementation of the approach // Utility function to print // the contents of the array function printArr(arr, n) { for (let i = 0; i < n; i++) document.write(arr[i] + " " ); } // To do two way sort. Make comparator function // for the inbuilt sort function of c++ such that // odd numbers are placed before even in descending // and ascending order respectively function compare(a, b) { // If both numbers are even, // smaller number should // be placed at lower index if (a % 2 == 0 && b % 2 == 0 && a < b) return -1; // If both numbers are odd larger number // should be placed at lower index if (a % 2 != 0 && b % 2 != 0 && b > a) return 1; // If a is odd and b is even, // a should be placed before b if (a % 2 != 0) return -1; // If b is odd and a is even, // b should be placed before a return 1; } // Driver code var arr = [1, 3, 2, 7, 5, 4]; var n = arr.length; // Sort the array arr.sort(compare); // Print the sorted array printArr(arr, n); // This code is contributed by Potta Lokesh </script> |
7 5 3 1 2 4
Thanks to Amandeep Singh for suggesting this solution.
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