Array Insertion at End in DSA Go - Build from Scratch

Array Insertion at End

📖 Scenario: You are managing a list of daily temperatures recorded in a weather app. Each day, a new temperature is added at the end of the list.

🎯 Goal: Build a program that stores initial temperatures in an array, sets the new temperature to add, inserts it at the end of the array, and then prints the updated array.

📋 What You'll Learn

Create an array called temps with the exact values 20, 22, 19, 23

Create a variable called newTemp and set it to 25

Append newTemp to the end of temps using Go slice append

Print the updated temps array

💡 Why This Matters

🌍 Real World

Weather apps and many other programs often need to add new data points to a list as new information arrives.

💼 Career

Understanding how to add elements to arrays or lists is a fundamental skill for software developers working with data collections.

1

Create the initial array

Create an array called temps with the exact values 20, 22, 19, 23.

DSA Go

# Create an array called temps with values 20, 22, 19, 23
# Your code here

Hint

Use temps := []int{20, 22, 19, 23} to create the array.

2

Set the new temperature

Create a variable called newTemp and set it to 25.

DSA Go

package main

import "fmt"

func main() {
    temps := []int{20, 22, 19, 23}
    // Create a variable newTemp and set it to 25
    // Your code here
}

Hint

Use newTemp := 25 to create the variable.

3

Append the new temperature

Append newTemp to the end of the temps array using Go's append function.

DSA Go

package main

import "fmt"

func main() {
    temps := []int{20, 22, 19, 23}
    newTemp := 25
    // Append newTemp to temps
    // Your code here
}

Hint

Use temps = append(temps, newTemp) to add the new temperature.

4

Print the updated array

Print the updated temps array using fmt.Println.

DSA Go

package main

import "fmt"

func main() {
    temps := []int{20, 22, 19, 23}
    newTemp := 25
    temps = append(temps, newTemp)
    // Print temps
    // Your code here
}

Hint

Use fmt.Println(temps) to print the array.

Practice

1. What happens when you insert an element at the end of a fixed-size array in Go?

easy

A. You cannot insert because arrays have fixed size

B. The element replaces the first element

C. The element is added and array size increases automatically

D. The array is converted to a slice automatically

Solution

1. Step 1: Understand Go array size

   Arrays in Go have a fixed size defined at declaration and cannot grow.

2. Step 2: Effect of insertion at end

   Since size is fixed, you cannot add new elements beyond the declared size.

3. Final Answer:

   You cannot insert because arrays have fixed size -> Option A

4. Quick Check:

   Fixed size array = no insertion beyond size [OK]

Hint: Arrays have fixed size; no automatic growth on insertion [OK]

Common Mistakes:

• Thinking arrays can grow automatically
• Confusing arrays with slices
• Assuming insertion replaces last element

2. Which of the following is the correct way to append an element 10 to a slice named nums in Go?

easy

A. nums = nums + 10

B. nums.append(10)

C. append(nums, 10)

D. nums = append(nums, 10)

Solution

1. Step 1: Recall Go slice append syntax

   In Go, append returns a new slice with the element added, so assignment is needed.

2. Step 2: Check each option

   nums = append(nums, 10) correctly assigns the result of append to nums. Others are invalid syntax or missing assignment.

3. Final Answer:

   nums = append(nums, 10) -> Option D

4. Quick Check:

   Use append with assignment to add element [OK]

Hint: Always assign append result back to slice variable [OK]

Common Mistakes:

• Not assigning append result back
• Using method call syntax like nums.append()
• Trying to add with + operator

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

nums := []int{1, 2, 3}
nums = append(nums, 4)
fmt.Println(nums)

medium

A. [1 2 3]

B. [4 1 2 3]

C. [1 2 3 4]

D. Compilation error

Solution

1. Step 1: Understand initial slice and append

   nums starts as [1 2 3]. append(nums, 4) adds 4 at the end.

2. Step 2: Print the updated slice

   After append, nums becomes [1 2 3 4], which is printed.

3. Final Answer:

   [1 2 3 4] -> Option C

4. Quick Check:

   Appending 4 adds it at end [OK]

Hint: append adds element at end, print shows updated slice [OK]

Common Mistakes:

• Expecting original slice without new element
• Thinking append adds at start
• Confusing slice with array syntax

4. Identify the error in the following Go code that tries to insert 5 at the end of an array:

arr := [3]int{1, 2, 3}
arr = append(arr, 5)
fmt.Println(arr)

medium

A. Cannot use append on array; append works only on slices

B. Array size is too small; must declare larger array

C. Missing import for fmt package

D. Syntax error in array declaration

Solution

1. Step 1: Check type of arr

   arr is declared as an array [3]int, which has fixed size and no append method.

2. Step 2: Understand append usage

   append works only on slices, not arrays. Using append on array causes error.

3. Final Answer:

   Cannot use append on array; append works only on slices -> Option A

4. Quick Check:

   append requires slice, not array [OK]

Hint: append works only on slices, not fixed-size arrays [OK]

Common Mistakes:

• Trying to append to fixed-size array
• Ignoring difference between array and slice
• Assuming append auto-converts array to slice

5. Given a slice data := []int{2, 4, 6}, which code snippet correctly inserts the value 8 at the end and then doubles all elements?

hard

A. data = append(data, 8)
for _, v := range data {
v *= 2
}
fmt.Println(data)

B. data = append(data, 8)
for i := range data {
data[i] *= 2
}
fmt.Println(data)

C. data = append(data, 8)
for i := 0; i < len(data); i++ {
data[i] = data[i] + 2
}
fmt.Println(data)

D. data = append(data, 8)
for i := range data {
data[i] = data[i] / 2
}
fmt.Println(data)

Solution

1. Step 1: Append 8 to slice

   data = append(data, 8) adds 8 at the end, making data [2 4 6 8].

2. Step 2: Double each element correctly

   Using for i := range data and data[i] *= 2 doubles each element in place.

3. Step 3: Check other options

   data = append(data, 8) for _, v := range data { v *= 2 } fmt.Println(data) doubles copy of value, not original slice. Options C and D do wrong math.

4. Final Answer:

   data = append(data, 8) for i := range data { data[i] *= 2 } fmt.Println(data) -> Option B

5. Quick Check:

   Append then modify elements by index [OK]

Hint: Modify slice elements by index, not by value copy [OK]

Common Mistakes:

• Modifying value copy in range instead of slice element
• Using wrong arithmetic operation
• Not assigning append result back