Array Deletion at Beginning in DSA Go - Build from Scratch

Array Deletion at Beginning

📖 Scenario: You are managing a queue of customers waiting in line at a store. The queue is represented as an array where the first customer is at the beginning of the array.When a customer is served, they leave the queue from the beginning.

🎯 Goal: Build a program that removes the first customer from the queue (array) and shows the updated queue.

📋 What You'll Learn

Create an array called queue with these exact customer names: "Alice", "Bob", "Charlie", "Diana", "Ethan"

Create a variable called servedCustomer to hold the name of the customer who is served (removed from the beginning)

Remove the first customer from the queue and assign their name to servedCustomer

Print the name of the served customer and the updated queue in the format: "Served: Alice" and "Queue: [Bob Charlie Diana Ethan]"

💡 Why This Matters

🌍 Real World

Queues are common in real life, like lines at stores or tasks waiting to be processed. Managing them with arrays helps in many programs.

💼 Career

Understanding how to remove elements from arrays is important for jobs involving data processing, backend development, and system design.

1

Create the initial queue array

Create an array called queue with these exact customer names: "Alice", "Bob", "Charlie", "Diana", "Ethan"

DSA Go

# Create the queue array with the given customer names
# Your code here

Hint

Use a slice of strings and assign the exact names in order.

2

Create a variable to hold the served customer

Create a variable called servedCustomer of type string to hold the name of the customer who will be served

DSA Go

package main

import "fmt"

func main() {
    queue := []string{"Alice", "Bob", "Charlie", "Diana", "Ethan"}
    // Create servedCustomer variable here
    // Your code here
}

Hint

Declare servedCustomer as a string variable without assigning a value yet.

3

Remove the first customer and assign to servedCustomer

Remove the first customer from the queue and assign their name to servedCustomer. Update queue to remove that first customer.

DSA Go

package main

import "fmt"

func main() {
    queue := []string{"Alice", "Bob", "Charlie", "Diana", "Ethan"}
    var servedCustomer string
    // Remove first customer and update queue
    // Your code here
}

Hint

Assign the first element of queue to servedCustomer. Then slice queue from index 1 to remove the first customer.

4

Print the served customer and updated queue

Print the name of the served customer using fmt.Println("Served:", servedCustomer) and then print the updated queue using fmt.Println("Queue:", queue)

DSA Go

package main

import "fmt"

func main() {
    queue := []string{"Alice", "Bob", "Charlie", "Diana", "Ethan"}
    var servedCustomer string
    servedCustomer = queue[0]
    queue = queue[1:]
    // Print served customer and updated queue
    // Your code here
}

Hint

Use fmt.Println twice: once for the served customer and once for the updated queue.

Practice

1. What happens to the array [10, 20, 30, 40] after deleting the first element at the beginning?

easy

A. [40]

B. [10, 20, 30]

C. [20, 30, 40]

D. [30, 40]

Solution

1. Step 1: Understand deletion at beginning

   Deleting the first element removes the element at index 0, which is 10.

2. Step 2: Shift remaining elements left

   The remaining elements 20, 30, 40 shift left to fill the gap, resulting in [20, 30, 40].

3. Final Answer:

   [20, 30, 40] -> Option C

4. Quick Check:

   Remove first element = [20, 30, 40] [OK]

Hint: Remove first element, shift left, rest remain [OK]

Common Mistakes:

• Removing last element instead of first
• Not shifting elements left after deletion
• Leaving the first element in place

2. Which of the following Go code snippets correctly deletes the first element from a slice arr?

easy

A. arr = append(arr, 0)

B. arr = arr[1:]

C. arr = arr[:len(arr)-1]

D. arr = arr[0:]

Solution

1. Step 1: Understand slice slicing syntax

   In Go, arr[1:] creates a slice from index 1 to end, effectively removing the first element.

2. Step 2: Check other options

   arr[:len(arr)-1] removes last element, append(arr, 0) adds element, arr[0:] returns full slice.

3. Final Answer:

   arr = arr[1:] -> Option B

4. Quick Check:

   Slice from index 1 removes first element [OK]

Hint: Use arr = arr[1:] to drop first element [OK]

Common Mistakes:

• Using arr[:len(arr)-1] deletes last element
• Appending instead of slicing
• Using arr[0:] which does not delete anything

3. What is the output of the following Go code?

arr := []int{5, 10, 15, 20}
arr = arr[1:]
fmt.Println(arr)

medium

A. [5 10 15 20]

B. []

C. [15 20]

D. [10 15 20]

Solution

1. Step 1: Initial array elements

   arr starts as [5, 10, 15, 20].

2. Step 2: Slice from index 1

   arr = arr[1:] removes first element 5, resulting in [10, 15, 20].

3. Final Answer:

   [10 15 20] -> Option D

4. Quick Check:

   arr[1:] drops first element [OK]

Hint: arr[1:] slices from second element onward [OK]

Common Mistakes:

• Printing original array without slicing
• Confusing arr[:1] with arr[1:]
• Expecting output with commas instead of spaces

4. The following Go code tries to delete the first element from arr. What is the error?

arr := []int{1, 2, 3, 4}
arr = arr[0:len(arr)]
fmt.Println(arr)

medium

A. No deletion happens; array remains unchanged

B. Syntax error due to incorrect slicing

C. Runtime panic due to out of range slice

D. Deletes last element instead of first

Solution

1. Step 1: Analyze slicing range

   arr[0:len(arr)] returns the full slice unchanged.

2. Step 2: Check effect on array

   Since no elements are removed, arr remains [1, 2, 3, 4].

3. Final Answer:

   No deletion happens; array remains unchanged -> Option A

4. Quick Check:

   Slicing full range keeps array same [OK]

Hint: arr[0:len(arr)] returns full slice, no deletion [OK]

Common Mistakes:

• Assuming slicing deletes first element
• Expecting runtime error from slicing
• Confusing slicing syntax with deletion

5. Given a slice arr := []int{7, 14, 21, 28, 35}, write the Go code to delete the first two elements and print the resulting slice.

hard

A. arr = arr[2:]
fmt.Println(arr)

B. arr = arr[:len(arr)-2]
fmt.Println(arr)

C. arr = arr[1:]
fmt.Println(arr)

D. arr = append(arr[:2], arr[2:]...)
fmt.Println(arr)

Solution

1. Step 1: Understand deletion of first two elements

   To delete first two elements, slice from index 2 to end: arr[2:].

2. Step 2: Verify other options

   arr[:len(arr)-2] removes last two elements, arr[1:] removes only first element, append(arr[:2], arr[2:]...) reconstructs the original slice.

3. Final Answer:

   arr = arr[2:] fmt.Println(arr) -> Option A

4. Quick Check:

   Slice from index 2 removes first two elements [OK]

Hint: Use arr = arr[2:] to remove first two elements [OK]

Common Mistakes:

• Removing last elements instead of first
• Removing only one element instead of two
• Using append unnecessarily for simple slicing