﻿ C Program: Rearrange an array such that arr[i]=i - w3resource

# C Exercises: Rearrange an array such that arr[i]=i

## C Array: Exercise-101 with Solution

Write a program in C to rearrange an array such that arr[i]=i.

N.B.: Given array contains N elements, from 0 to N – 1. All elements within the range may not be present in the array. There will be -1 if an element within the range is not present in the array.

Expected Output:
The given array is:
2 5 -1 6 -1 8 7 -1 9 1
The new array is: -1 1 2 -1 -1 5 6 7 8 9

The task is to write a C program that rearranges an array such that each element at index i equals i. If an element within the range [0, N-1] is not present in the array, it should be represented by -1. The program should iterate through the array, reposition elements to satisfy the condition arr[i] = i , and display the modified array.

Sample Solution:

C Code:

``````#include<stdio.h>

// Function to rearrange the array
int arrayRearrange(int arr1[], int l)
{
for (int i = 0; i < l; i++)
{
if (arr1[i] != -1 && arr1[i] != i)
{
int x = arr1[i];
// Swap elements until an element is -1 or the same as its index
while (arr1[x] != -1 && arr1[x] != x)
{
int y = arr1[x];
arr1[x] = x;
x = y;
}
arr1[x] = x;
if (arr1[i] != i)
{
arr1[i] = -1; // Set the element to -1 if it doesn't match its index
}
}
}
}

int main()
{
int arr1[] = { 2, 5, -1, 6, -1, 8, 7, -1, 9, 1 };
int n = sizeof(arr1) / sizeof(arr1[0]);
int i = 0;

// Print the original array
printf("The given array is:  \n");
for(i = 0; i < n; i++)
{
printf("%d  ", arr1[i]);
}
printf("\n");

// Rearrange the array and print the new array
printf("The new array is: ");
arrayRearrange(arr1, n);
for (int i = 0; i < n; i++)
printf("%d  ",arr1[i]);
}
```
```

Output:

```The given array is:
2  5  -1  6  -1  8  7  -1  9  1
The new array is: -1  1  2  -1  -1  5  6  7  8  9
```

Visual Presentation:

Flowchart:

C Programming Code Editor:

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