Insert an element into the array at user defined position.

Learn how to insert an element at any position in an array

array_insertion.c

#include <stdio.h>

int main() {
    int arr[20], n, i, pos, value;

    // Input current size of array
    printf("Enter number of elements (max 19): ");
    scanf("%d", &n);

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

    // Input value and position to insert
    printf("Enter the element to insert: ");
    scanf("%d", &value);
    printf("Enter the position (0 to %d): ", n);
    scanf("%d", &pos);

    // Shift elements to the right
    for(i = n; i > pos; i--) {
        arr[i] = arr[i - 1];
    }

    // Insert the new value
    arr[pos] = value;
    n++;  // increase size

    // Display updated array
    printf("\nArray after insertion:\n");
    for(i = 0; i < n; i++) {
        printf("arr[%d] = %d\n", i, arr[i]);
    }

    return 0;
}

🧾 Step-by-Step Explanation

🔹 Step 1: Include Header File

#include <stdio.h>

This header provides essential input/output functions:

• printf() for displaying output
• scanf() for reading user input
• Other standard I/O operations

🔹 Step 2: Declare Variables and Array

int arr[20], n, i, pos, value;

• arr[20]: Array with maximum capacity of 20 elements
• n: Current number of elements in the array
• pos: Position where new element will be inserted
• value: The element to be inserted
• i: Loop counter variable

🔹 Step 3: Input Array Elements

printf("Enter number of elements (max 19): ");
scanf("%d", &n);

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

• First gets the current size of the array (n)
• Then collects each element from the user
• Stores elements sequentially in the array
• Limits to 19 elements to leave space for insertion

🔹 Step 4: Input Position and Value to Insert

printf("Enter the element to insert: ");
scanf("%d", &value);
printf("Enter the position (0 to %d): ", n);
scanf("%d", &pos);

• Gets the new value to be inserted
• Gets the insertion position (0 to n)
• Valid positions are between 0 and current size (n)

🔹 Step 5: Shift Elements to the Right

for(i = n; i > pos; i--) {
    arr[i] = arr[i - 1];
}

• Starts from the end of the array
• Moves each element one position to the right
• Creates space at the insertion point
• Works backwards to avoid overwriting data

🔹 Step 6: Insert the New Value

arr[pos] = value;
n++;

• Places the new value at the specified position
• Increments the array size counter (n)
• Maintains array integrity

🔹 Step 7: Display the Updated Array

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

• Prints all elements including the new insertion
• Shows both index and value for each element
• Verifies the successful insertion

🧪 Sample Output

Enter number of elements (max 19): 5
Enter 5 elements:
arr[0]: 10
arr[1]: 20
arr[2]: 30
arr[3]: 40
arr[4]: 50
Enter the element to insert: 99
Enter the position (0 to 5): 2

Array after insertion:
arr[0] = 10
arr[1] = 20
arr[2] = 99
arr[3] = 30
arr[4] = 40
arr[5] = 50

📌 Key Concepts Covered

Array Operations

Manipulating fixed-size collections of elements in memory

Element Insertion

Adding new elements at specific positions by shifting existing elements

Right Shifting

Moving array elements to higher indices to create space for insertion

Position Validation

Ensuring insertion position is within valid bounds (0 to current size)

Size Management

Tracking and updating the current number of elements in the array