Rearrange an array so that 'arr' becomes 'i' if 'arr' is 'j' in C++

Let’s look at various input and output scenarios for this situation - h2>

Input− int arr[] = {3, 4, 1, 2, 0}

Output− Array before sorting: 3 4 1 2 0 Rearrange the array so that arr[j] becomes i. If arr[i] is j, it is: 4 2 3 0 1

Explanation− We get an integer of size Array 6 and all elements in the array with values ​​less than 6. Now, we will rearrange the array, i.e. arr[1] is 4, arr[4] = 1; arr[2] is 1, arr[1] = 2; arr[3] is 2. arr[2] = 3; arr[4] is 0, arr[0]=4. Therefore, the final array is 4 2 3 0 1.

Input t− int arr[] = {2, 0, 1, 3}

Output− Array before arrangement: 2 0 1 3 Rearrange the array so that arr[j] becomes i, if arr[i] is j, then: 1 2 0 3

Explanation− We get an integer of size 6 array and the value of all elements in the array is less than 6. Now, we will rearrange the array, i.e. arr[0] is 2, arr[2] = 0; arr[1] is 0, arr[0] = 1; arr[2] is 1, arr[1] = 2; arr[3] is 3, arr[3] = 3. Therefore, the final array is 1 2 0 3.

The method used in the following program is as follows

• Input an array of integer type elements and calculate the size of the array.

• Print the array before arranging it and call the function Rearrangement(arr, size)

• In the function Rearrangement(arr, size)

  • Create an array ptr[] of integer type values ​​with the same size as the array arr[].

  • Start looping FOR from i to 0 until i is less than size. Inside the loop, set ptr[arr[i]] to i.

  • Start looping FOR from i to 0 until i is less than size. Inside the loop, set arr[i] to ptr[i].

• #Print the rearranged array.

Example

#include <bits/stdc++.h>
using namespace std;
void Rearrangement(int arr[], int size){
   int ptr[size];
   for(int i = 0; i < size; i++){
      ptr[arr[i]] = i;
   }
   for(int i = 0; i < size; i++){
      arr[i] = ptr[i];
   }
}
int main(){
   //input an array
   int arr[] = {3, 4, 1, 2, 0};
   int size = sizeof(arr) / sizeof(arr[0]);
   //print the original Array
   cout<<"Array before Arrangement: ";
   for (int i = 0; i < size; i++){
      cout << arr[i] << " ";
   }
   //calling the function to rearrange the array
   Rearrangement(arr, size);
   //print the array after rearranging the values
   cout<<"\nRearrangement of an array such that &lsquo;arr[j]&rsquo; becomes &lsquo;i&rsquo; if &lsquo;arr[i]&rsquo; is &lsquo;j&rsquo; is: ";
   for(int i = 0; i < size; i++){
      cout<< arr[i] << " ";
   }
   return 0;
}

Output

If we run the above code it will generate the following output

Array before Arrangement: 3 4 1 2 0
Rearrangement of an array such that ‘arr[j]’ becomes ‘i’ if ‘arr[i]’ is ‘j’ is: 4 2 3 0 1

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