Replace every elements in the array by its frequency in the array
Given an array of integers, replace every element by its frequency in the array.
Examples:
Input : arr[] = { 1, 2, 5, 2, 2, 5 }
Output : 1 3 2 3 3 2
Input : arr[] = { 4 5 4 5 6 6 6 }
Output : 2 2 2 2 3 3 3
Approach:
- Take a hash map, which will store the frequency of all the elements in the array.
- Now, traverse once again.
- Now, replace all the elements by their frequency.
- Print the modified array.
Implementation:
C++
#include "iostream"
#include "unordered_map"
using namespace std;
void ReplaceElementsByFrequency( int arr[], int n)
{
unordered_map< int , int > mp;
for ( int i = 0; i < n; ++i) {
mp[arr[i]]++;
}
for ( int i = 0; i < n; ++i) {
arr[i] = mp[arr[i]];
}
}
int main()
{
int arr[] = { 1, 2, 5, 2, 2, 5 };
int n = sizeof (arr) / sizeof (arr[0]);
ReplaceElementsByFrequency(arr, n);
for ( int i = 0; i < n; ++i) {
cout << arr[i] << " " ;
}
return 0;
}
|
Java
import java.util.HashMap;
class GFG {
static void ReplaceElementsByFrequency( int arr[], int n) {
HashMap<Integer, Integer> mp = new HashMap<Integer, Integer>();
for ( int i = 0 ; i < n; ++i) {
if (mp.get(arr[i]) == null ) {
mp.put(arr[i], 1 );
} else {
mp.put(arr[i], (mp.get(arr[i]) + 1 ));
}
}
for ( int i = 0 ; i < n; ++i) {
if (mp.get(arr[i]) != null ) {
arr[i] = mp.get(arr[i]);
}
}
}
public static void main(String[] args) {
int arr[] = { 1 , 2 , 5 , 2 , 2 , 5 };
int n = arr.length;
ReplaceElementsByFrequency(arr, n);
for ( int i = 0 ; i < n; ++i) {
System.out.print(arr[i] + " " );
}
}
}
|
Python3
def ReplaceElementsByFrequency(arr, n):
mp = {i: 0 for i in range ( len (arr))}
for i in range (n):
mp[arr[i]] + = 1
for i in range (n):
arr[i] = mp[arr[i]]
if __name__ = = '__main__' :
arr = [ 1 , 2 , 5 , 2 , 2 , 5 ]
n = len (arr)
ReplaceElementsByFrequency(arr, n);
for i in range (n):
print (arr[i], end = " " )
|
C#
using System;
using System.Collections.Generic;
class GFG
{
static void ReplaceElementsByFrequency( int []arr, int n)
{
Dictionary< int , int > mp = new Dictionary< int , int >();
for ( int i = 0; i < n; ++i)
{
if (!mp.ContainsKey(arr[i]))
{
mp.Add(arr[i], 1);
}
else
{
var a = mp[arr[i]] + 1;
mp.Remove(arr[i]);
mp.Add(arr[i], a);
}
}
for ( int i = 0; i < n; ++i)
{
if (mp[arr[i]] != 0)
{
arr[i] = mp[arr[i]];
}
}
}
public static void Main(String[] args)
{
int []arr = {1, 2, 5, 2, 2, 5};
int n = arr.Length;
ReplaceElementsByFrequency(arr, n);
for ( int i = 0; i < n; ++i)
{
Console.Write(arr[i] + " " );
}
}
}
|
Javascript
<script>
function ReplaceElementsByFrequency(arr, n)
{
let mp = new Map();
for (let i = 0; i < n; ++i)
{
if (mp.get(arr[i]) == null )
{
mp.set(arr[i], 1);
}
else
{
mp.set(arr[i], (mp.get(arr[i]) + 1));
}
}
for (let i = 0; i < n; ++i)
{
if (mp.get(arr[i]) != null )
{
arr[i] = mp.get(arr[i]);
}
}
}
let arr = [ 1, 2, 5, 2, 2, 5 ];
let n = arr.length;
ReplaceElementsByFrequency(arr, n);
for (let i = 0; i < n; ++i)
{
document.write(arr[i] + " " );
}
</script>
|
Time Complexity: O(N)
Auxiliary Space: O(N) because extra space is being used for unordered_map mp
Last Updated :
17 Sep, 2022
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