C Exercises: Rearrange an array so that arr[i] becomes arr[arr[i]] from an array of size n and elements are in the range 0 to n-1

Last update on March 18 2025 13:20:58 (UTC/GMT +8 hours)

90. Rearrange Array so that arr[i] = arr[arr[i]]

Given an array of size n such that every element is in the range from 0 to n-1. Write a program in C to rearrange the given array so that arr[i] becomes arr[arr[i]].

Expected Output:
The Original array is
2 1 4 3 0 The modified array is:
4 1 0 3 2

The problem involves writing a C program to rearrange an array of size n, where each element is within the range from 0 to n-1, so that each element at index i becomes the value at index arr[i] . The program should update the array in place to achieve this transformation. The output will display the original array and the modified array after rearrangement.

Sample Solution:

C Code:

#include<stdio.h>

// Function to rearrange the elements of an array based on given conditions
void arrayArrange(int arr1[], int n) 
{ 
    // Rearranging elements by using index-based calculation
    for (int i = 0; i < n; i++) {
        // Adding the modified value at the current index
        // Modified value is calculated using the modulo operation and multiplication by 'n'
        arr1[i] += (arr1[arr1[i]] % n) * n;
    }

    // Adjusting elements by dividing them by 'n' to obtain the original values
    for (int i = 0; i < n; i++) {
        arr1[i] /= n;
    }
} 

// Function to print the elements of an array
void arrayPrinting (int arr1[], int n) 
{ 
    for (int i = 0; i < n; i++) {
        printf("%d  ", arr1[i]); 
    }
    printf("\n"); 
} 

// Main function
int main() 
{ 
    int arr1[] = {2, 1, 4, 3, 0}; 
    int n = sizeof(arr1) / sizeof(arr1[0]); 

    printf("The Original array is \n"); 
    arrayPrinting(arr1, n); 

    // Rearranging the array elements
    arrayArrange(arr1, n); 

    printf("The modified array is: \n"); 
    arrayPrinting(arr1, n); 
    return 0; 
}

Output:

The Original array is 
2  1  4  3  0  
The modified array is: 
4  1  0  3  2

Flowchart:/p>

For more Practice: Solve these Related Problems:

• Write a C program to rearrange an array so that each element becomes the element at the index of its current value.
• Write a C program to update an array such that arr[i] becomes arr[arr[i]] without using extra memory.
• Write a C program to rearrange an array based on the mapping defined by its elements and then verify the transformation.
• Write a C program to perform the rearrangement operation and then print both the original and modified arrays.

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