Trust Coding : Programming: Write a program in C to rotate the elements of an array to the left by two positions (first element becomes second last).

Rotate Array Elements to the Left by Two Positions in C

In this tutorial, we will write a C program to rotate the elements of an array to the left by two positions.

Problem Statement

Write a C program to rotate the elements of an array to the left by two positions. After rotation:

The first element becomes the second last.
The second element becomes the last.
All other elements shift two positions to the left.

Example

Original Array: 1 2 3 4 5
After Rotation: 3 4 5 1 2

Algorithm

Store the first two elements in temporary variables.
Shift the remaining elements two positions to the left.
Place the stored elements at the end of the array.

C Program


#include <stdio.h>

int main() {
    int arr[100], n, i;
    int temp1, temp2;

    printf("Enter number of elements: ");
    scanf("%d", &n);

    printf("Enter %d elements:\n", n);
    for(i = 0; i < n; i++) {
        scanf("%d", &arr[i]);
    }

    // Check if array has at least 2 elements
    if(n < 2) {
        printf("Rotation not possible.\n");
        return 0;
    }

    // Store first two elements
    temp1 = arr[0];
    temp2 = arr[1];

    // Shift elements left by 2 positions
    for(i = 0; i < n - 2; i++) {
        arr[i] = arr[i + 2];
    }

    // Place stored elements at the end
    arr[n - 2] = temp1;
    arr[n - 1] = temp2;

    printf("Array after left rotation by 2 positions:\n");
    for(i = 0; i < n; i++) {
        printf("%d ", arr[i]);
    }

    return 0;
}

Explanation

Step 1: Input

The user enters the number of elements and the array values.

Step 2: Store First Two Elements

We store the first two elements in temporary variables:


temp1 = arr[0];
temp2 = arr[1];

Step 3: Shift Elements

We move each element two positions left:


for(i = 0; i < n - 2; i++) {
    arr[i] = arr[i + 2];
}

Step 4: Place Stored Elements at End

Finally, we place the stored elements at the last two positions:


arr[n - 2] = temp1;
arr[n - 1] = temp2;

Time Complexity

The program uses a single loop to shift elements. Therefore, the time complexity is O(n).

Trust Coding : Programming

Write a program in C to rotate the elements of an array to the left by two positions (first element becomes second last).