Sort an array according to absolute difference with given value
Given an array of N distinct elements and a number x, arrange array elements according to the absolute difference with x, i. e., an element having minimum difference comes first, and so on.
Note: If two or more elements are at equal distances arrange them in the same sequence as in the given array.
Examples:
Input: x = 7, arr[] = {10, 5, 3, 9, 2}
Output: arr[] = {5, 9, 10, 3, 2}
Explanation:
7 – 10 = 3(abs)
7 – 5 = 2
7 – 3 = 4
7 – 9 = 2(abs)
7 – 2 = 5
So according to the difference with X,
elements are arranged as 5, 9, 10, 3, 2.Input: x = 6, arr[] = {1, 2, 3, 4, 5}
Output: arr[] = {5, 4, 3, 2, 1}
Sort an array according to absolute difference with a given value using self-balancing BST:
To solve the problem follow the below idea:
The idea is to use a self-balancing binary search tree. We traverse the input array and for every element, we find its difference with x and store the difference as key and element as the value in a self-balancing binary search tree. Finally, we traverse the tree and print its inorder traversal which is the required output.
Approach for C++ Implementation:
In C++, self-balancing-binary-search-tree is implemented by set, map, and multimap. We can’t use set here as we have key-value pairs (not only keys). We also can’t directly use map also as a single key can belong to multiple values and map allows a single value for a key. So we use multimap which stores key-value pairs and can have multiple values for a key.
Follow the below steps to solve the problem:
- Store the values in the multimap with the difference with X as key.
- In multimap, the values will be already in sorted order according to key i.e. difference with X because it implements self-balancing-binary-search-tree internally.
- Update all the values of an array with the values of the map so that the array has the required output.
Below is the implementation of the above approach:
C++
// C++ program to sort an array according absolute // difference with x. #include <bits/stdc++.h> using namespace std; // Function to sort an array according absolute // difference with x. void rearrange( int arr[], int n, int x) { multimap< int , int > m; multimap< int , int >::iterator it; // Store values in a map with the difference // with X as key for ( int i = 0; i < n; i++) m.insert(make_pair( abs (x - arr[i]), arr[i])); // Update the values of array int i = 0; for (it = m.begin(); it != m.end(); it++) arr[i++] = (*it).second; } // Function to print the array void printArray( int arr[], int n) { for ( int i = 0; i < n; i++) cout << arr[i] << " " ; } // Driver code int main() { int arr[] = { 10, 5, 3, 9, 2 }; int n = sizeof (arr) / sizeof (arr[0]); int x = 7; // Function call rearrange(arr, n, x); printArray(arr, n); return 0; } |
Java
// Java program to sort an array according absolute // difference with x. import java.io.*; import java.util.*; class GFG { // Function to sort an array according absolute // difference with x. static void rearrange( int [] arr, int n, int x) { TreeMap<Integer, ArrayList<Integer> > m = new TreeMap<>(); // Store values in a map with the difference // with X as key for ( int i = 0 ; i < n; i++) { int diff = Math.abs(x - arr[i]); if (m.containsKey(diff)) { ArrayList<Integer> al = m.get(diff); al.add(arr[i]); m.put(diff, al); } else { ArrayList<Integer> al = new ArrayList<>(); al.add(arr[i]); m.put(diff, al); } } // Update the values of array int index = 0 ; for (Map.Entry entry : m.entrySet()) { ArrayList<Integer> al = m.get(entry.getKey()); for ( int i = 0 ; i < al.size(); i++) arr[index++] = al.get(i); } } // Function to print the array static void printArray( int [] arr, int n) { for ( int i = 0 ; i < n; i++) System.out.print(arr[i] + " " ); } // Driver code public static void main(String args[]) { int [] arr = { 10 , 5 , 3 , 9 , 2 }; int n = arr.length; int x = 7 ; // Function call rearrange(arr, n, x); printArray(arr, n); } } // This code is contributed by rachana soma |
Python3
# Python3 program to sort an # array according absolute # difference with x. # Function to sort an array # according absolute difference # with x. def rearrange(arr, n, x): m = {} # Store values in a map # with the difference # with X as key for i in range (n): m[arr[i]] = abs (x - arr[i]) m = {k: v for k, v in sorted (m.items(), key = lambda item: item[ 1 ])} # Update the values of array i = 0 for it in m.keys(): arr[i] = it i + = 1 # Function to print the array def printArray(arr, n): for i in range (n): print (arr[i], end = " " ) # Driver code if __name__ = = "__main__" : arr = [ 10 , 5 , 3 , 9 , 2 ] n = len (arr) x = 7 # Function call rearrange(arr, n, x) printArray(arr, n) # This code is contributed by Chitranayal |
C#
// C# program to sort an array according absolute // difference with x. using System; using System.Collections.Generic; public class GFG { // Function to sort an array according absolute // difference with x. static void rearrange( int [] arr, int n, int x) { SortedDictionary< int , List< int > > m = new SortedDictionary< int , List< int > >(); // Store values in a map with the difference // with X as key for ( int i = 0; i < n; i++) { int diff = Math.Abs(x - arr[i]); if (m.ContainsKey(diff)) { List< int > al = m; al.Add(arr[i]); m = al; } else { List< int > al = new List< int >(); al.Add(arr[i]); m.Add(diff, al); } } // Update the values of array int index = 0; foreach ( int entry in m.Keys) { List< int > al = m[entry]; for ( int i = 0; i < al.Count; i++) arr[index++] = al[i]; } } // Function to print the array static void printArray( int [] arr, int n) { for ( int i = 0; i < n; i++) Console.Write(arr[i] + " " ); } // Driver code static public void Main() { int [] arr = { 10, 5, 3, 9, 2 }; int n = arr.Length; int x = 7; // Function call rearrange(arr, n, x); printArray(arr, n); } } // This code is contributed by avanitrachhadiya2155 |
Javascript
// JavaScript program to sort an array according absolute // difference with x. // Function to sort an array according absolute // difference with x. function rearrange(arr,n,x) { let m = new Map(); // Store values in a map with the difference // with X as key for (let i = 0; i < n; i++) { m.set(arr[i],Math.abs(x-arr[i])); } let m1 = new Map([...m.entries()].sort((a, b) => a[1] - b[1])); // Update the values of array let index = 0; for (let [key, value] of m1.entries()) { arr[index++] =key } } // Function to print the array function printArray(arr,n) { for (let i = 0; i < n; i++) document.write(arr[i] + " " ); } // Driver code let arr=[10, 5, 3, 9 ,2]; let n = arr.length; let x = 7; rearrange(arr, n, x); printArray(arr, n); // This code is contributed by ab2127 |
5 9 10 3 2
Time Complexity: O(N Log N)
Auxiliary Space: O(N)
This article is contributed by Sahil Chhabra.
Sort an array according to absolute difference with a given value using C++ STL:
In C++, we can use stable_sort(), and write a lambda expression for the custom comparator function. This solution is elegant and far easier to understand. The only challenge in writing the lambda expression is to send the value ‘x’ into the lambda expression to be able to use it inside the expression. This can be achieved either by operator overloading with the help of a class or using a much simpler capture.
Below is the implementation of the above approach:
C++
// CPP program for the above approach #include <bits/stdc++.h> using namespace std; void rearrange( int arr[], int n, int x) { /* We can send the value x into lambda expression as follows: [capture]() { //statements //capture value can be used inside } */ stable_sort(arr, arr + n, [x]( int a, int b) { if ( abs (a - x) < abs (b - x)) return true ; else return false ; }); } // Driver code int main() { int arr[] = { 10, 5, 3, 9, 2 }; int n = sizeof (arr) / sizeof (arr[0]); int x = 7; // Function call rearrange(arr, n, x); for ( int i = 0; i < n; i++) cout << arr[i] << " " ; return 0; } |
Java
import java.util.ArrayList; import java.util.Collections; import java.util.List; class GFG { static List<Integer> rearrange(List<Integer> arr, int n, int x) { Collections.sort( arr, (a, b) -> Math.abs(x - a) - Math.abs(x - b)); return arr; } // Driver code public static void main(String[] args) { List<Integer> arr = new ArrayList<>(); arr.add( 10 ); arr.add( 5 ); arr.add( 3 ); arr.add( 9 ); arr.add( 2 ); int n = arr.size(); int x = 7 ; // Function call arr = rearrange(arr, n, x); for ( int num : arr) { System.out.print(num + " " ); } } } // This code is contributed by phasing17. |
Python3
# Python3 program for the above approach def rearrange(arr, n, x): ''' We can send the value x into lambda expression as follows: [capture]() #statements #capture value can be used inside ''' arr.sort(key = lambda a: abs (a - x) ) # Driver code arr = [ 10 , 5 , 3 , 9 , 2 ]; n = len (arr) x = 7 ; # Function call rearrange(arr, n, x); print ( * arr) # This code is contributed by phasing17 |
C#
// C# program for the above approach using System; using System.Linq; using System.Collections.Generic; class GFG { static List< int > rearrange(List< int > arr, int n, int x) { /* We can send the value x into lambda expression as follows: [capture]() { //statements //capture value can be used inside } */ return arr.OrderBy(a => Math.Abs(x - a)).ToList(); } // Driver code public static void Main( string [] args) { List< int > arr = new List< int >{10, 5, 3, 9, 2}; int n = arr.Count; int x = 7; // Function call arr = rearrange(arr, n, x); foreach ( int num in arr) Console.Write(num + " " ); } } // This code is contributed by phasing17 |
Javascript
// JS program for the above approach function rearrange(arr, n, x) { /* We can send the value x into lambda expression as follows: [capture]() { //statements //capture value can be used inside } */ arr.sort( function (a, b) { return Math.abs(a - x) - Math.abs(b - x) }) } // Driver code let arr = [ 10, 5, 3, 9, 2 ]; let n = arr.length let x = 7; // Function call rearrange(arr, n, x); console.log(arr.join( " " )) // This code is contributed by phasing17 |
5 9 10 3 2
Time Complexity: O(N log N)
Auxiliary Space: O(1)
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