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}
Naive Approach-
The idea is to store all even in a separate array or vector and sort them in ascending order and then store all odd in a separate array or vector and sort them in descending order. Then replace all input array elements with those odd array/vector elements followed by even array/vector elements
Steps to implement-
- Declare two vectors odd and even to store odd and even elements
- Run a for loop on the input array to separately store odd and even elements into odd and even vector
- Then sort even elements in ascending order and odd elements in decreasing order
- Then, first copy odd elements into the original array and then even elements into that array
Code-
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) { //To store odd Numbers vector<int> odd; //To store Even Numbers vector<int> even; for(int i=0;i<n;i++){ //If number is even push them to even vector if(arr[i]%2==0){even.push_back(arr[i]);} //If number is odd push them to odd vector else{odd.push_back(arr[i]);} } //Sort even array in ascending order sort(even.begin(),even.end()); //Sort odd array in descending order sort(odd.begin(),odd.end(),greater<int>()); int i=0; //First store odd numbers to array for(int j=0;j<odd.size();j++){ arr[i]=odd[j]; i++; } //Then store even numbers to array for(int j=0;j<even.size();j++){ arr[i]=even[j]; i++; } } // 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; import java.util.List; import java.util.ArrayList; public class Main { // To do two way sort. // First sort even numbers in ascending order, // then odd numbers in descending order. public static void twoWaySort(int[] arr) { // To store odd Numbers List<Integer> odd = new ArrayList<>(); // To store Even Numbers List<Integer> even = new ArrayList<>(); for (int i = 0; i < arr.length; i++) { // If number is even, push them to the even list if (arr[i] % 2 == 0) { even.add(arr[i]); } // If number is odd, push them to the odd list else { odd.add(arr[i]); } } // Sort even list in ascending order Collections.sort(even); // Sort odd list in descending order Collections.sort(odd, Collections.reverseOrder()); int i = 0; // First store odd numbers in the array for (int j = 0; j < odd.size(); j++) { arr[i] = odd.get(j); i++; } // Then store even numbers in the array for (int j = 0; j < even.size(); j++) { arr[i] = even.get(j); i++; } } // Driver code public static void main(String[] args) { int[] arr = { 1, 3, 2, 7, 5, 4 }; twoWaySort(arr); for (int i = 0; i < arr.length; i++) { System.out.print(arr[i] + " "); } } } |
Python3
def twoWaySort(arr, n): # To store odd Numbers odd = [] # To store Even Numbers even = [] for i in range(n): # If number is even push them to even vector if arr[i] % 2 == 0: even.append(arr[i]) # If number is odd push them to odd vector else: odd.append(arr[i]) # Sort even array in ascending order even.sort() # Sort odd array in descending order odd.sort(reverse=True) i = 0 # First store odd numbers to array for j in range(len(odd)): arr[i] = odd[j] i += 1 # Then store even numbers to array for j in range(len(even)): arr[i] = even[j] i += 1 arr = [1, 3, 2, 7, 5, 4] n = len(arr) twoWaySort(arr, n) for i in range(n): print(arr[i], end=" ") |
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.Collections.Generic; using System.Linq; class Program { // 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) { // To store odd numbers List<int> odd = new List<int>(); // To store even numbers List<int> even = new List<int>(); for (int i = 0; i < n; i++) { // If number is even, push them to even list if (arr[i] % 2 == 0) { even.Add(arr[i]); } // If number is odd, push them to odd list else { odd.Add(arr[i]); } } // Sort even list in ascending order even.Sort(); // Sort odd list in descending order odd.Sort(); odd.Reverse(); int index = 0; // First store odd numbers in the array foreach(int number in odd) { arr[index] = number; index++; } // Then store even numbers in the array foreach(int number in even) { arr[index] = number; index++; } } // Driver code static void Main(string[] args) { int[] arr = { 1, 3, 2, 7, 5, 4 }; int n = arr.Length; TwoWaySort(arr, n); for (int i = 0; i < n; i++) { Console.Write(arr[i] + " "); } } } // This code is contributed by akshitaguprzj3 |
Javascript
// 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 // Function to do two-way sort. // First sort even numbers in ascending order, // then odd numbers in descending order. function twoWaySort(arr) { // To store odd numbers let odd = []; // To store even numbers let even = []; for (let i = 0; i < arr.length; i++) { // If number is even, push it to the even list if (arr[i] % 2 === 0) { even.push(arr[i]); } // If number is odd, push it to the odd list else { odd.push(arr[i]); } } // Sort the even list in ascending order even.sort((a, b) => a - b); // Sort the odd list in descending order odd.sort((a, b) => b - a); let index = 0; // First, store the odd numbers in the array for (let j = 0; j < odd.length; j++) { arr[index] = odd[j]; index++; } // Then, store the even numbers in the array for (let j = 0; j < even.length; j++) { arr[index] = even[j]; index++; } } // Driver code let arr = [1, 3, 2, 7, 5, 4]; twoWaySort(arr); console.log(arr.join(" ")); // This code is contributed by shivamgupta0987654321 |
Output
7 5 3 1 2 4
Time complexity: O(n + n log n) , for sorting even vector and odd vector and running a for loop
Auxiliary Space: O(n), because there are in total n elements in both the vector
Method 1 (Using Partition)
- Partition the input array such that all odd elements are moved to the 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).
Follow the below steps to implement the above idea:
- Initialize two variables l and r to 0 and n-1 respectively.
- Initialize a variable k to 0 which will count the number of odd elements in the array.
- Run a loop while l < r:
a. Find the first even number from the left side of the array by checking if arr[l] is even, if not increment l and k by 1.
b. Find the first odd number from the right side of the array by checking if arr[r] is odd, if not decrement r by 1.
c. Swap the even number at index l with the odd number at index r. - Sort the first k elements of the array in descending order using the in-built sort function with greater<int>() as the comparator.
- Sort the remaining n-k elements of the array in ascending order using the in-built sort function.
- The sorted array is now ready to be printed.
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 = 6arr = [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)
Auxiliary Space: 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.
Implementation:
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 |
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> |
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 ?> |
Output
7 5 3 1 2 4
Time complexity: O(n log n)
Auxiliary Space: 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> |
Output
7 5 3 1 2 4
Time complexity : O(n*logn) [sort function has average time complexity n*logn]
Auxiliary Space : O(1)
Thanks to Amandeep Singh for suggesting this solution.
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