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Rearrange an array such that ‘arr[j]’ becomes ‘i’ if ‘arr[i]’ is ‘j’ in C++
We are given a positive integer type array, let's say, arr[] of any given size such that elements in an array should value greater than 0 but less than the size of an array. The task is to rearrange an array in such a manner that if arr[j] is ‘j’ then arr[j] becomes ‘i’ and print the final result.
Let us see various input output scenarios for this −
Input − int arr[] = {3, 4, 1, 2, 0}
Outpu t− 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
Explanation − we are given an integer array of size 6 and all the elements in an array value 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.
Inpu t− int arr[] = {2, 0, 1, 3}
Output − Array before Arrangement: 2 0 1 3 Rearrangement of an array such that arr[j] becomes i if arr[i] is j is: 1 2 0 3
Explanation − we are given an integer array of size 6 and all the elements in an array value 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.
Approach used in the below program is as follows
Input an array of integer type elements and calculate the size of an array.
Print the array before arrangement and call the function Rearrangement(arr, size)
Inside the function Rearrangement(arr, size)
Create an array of integer type values as ptr[] of the same size as of array arr[].
Start loop FOR, from i to 0 till i less than size. Inside the loop, set ptr[arr[i]] to i.
Start loop FOR from i to 0 till i less than size. Inside the loop, set arr[i] to ptr[i].
Print the array after the rearrangement of values of an 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 ‘arr[j]’ becomes ‘i’ if ‘arr[i]’ is ‘j’ 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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