Array Insertion at End in DSA Rust - Build from Scratch

Array Insertion at End

📖 Scenario: You are managing a list of daily temperatures recorded in a weather app. Each day, you add the new temperature to the end of the list.

🎯 Goal: Build a Rust program that starts with a list of temperatures, adds a new temperature at the end, and then prints the updated list.

📋 What You'll Learn

Create a vector called temperatures with the exact values 20, 22, 19, 23

Create a variable called new_temp and set it to 21

Add new_temp to the end of temperatures using the push method

Print the temperatures vector after insertion

💡 Why This Matters

🌍 Real World

Adding new data points to a list is common in apps like weather trackers, stock price monitors, or any time series data.

💼 Career

Understanding how to manipulate arrays or vectors is essential for software developers working with data collections, especially in Rust programming.

1

Create the initial temperatures vector

Create a vector called temperatures with the exact values 20, 22, 19, 23.

DSA Rust

// Create a vector called temperatures with values 20, 22, 19, 23
// Your code here

Hint

Use let mut temperatures = vec![20, 22, 19, 23]; to create a mutable vector.

2

Create the new temperature variable

Create a variable called new_temp and set it to 21.

DSA Rust

fn main() {
    let mut temperatures = vec![20, 22, 19, 23];
    
    // Create a variable new_temp and set it to 21
    // Your code here
}

Hint

Use let new_temp = 21; to create the new temperature variable.

3

Add the new temperature to the vector

Use the push method to add new_temp to the end of the temperatures vector.

DSA Rust

fn main() {
    let mut temperatures = vec![20, 22, 19, 23];
    let new_temp = 21;
    
    // Add new_temp to the end of temperatures using push
    // Your code here
}

Hint

Use temperatures.push(new_temp); to add the new temperature.

4

Print the updated temperatures vector

Print the temperatures vector after adding the new temperature using println!.

DSA Rust

fn main() {
    let mut temperatures = vec![20, 22, 19, 23];
    let new_temp = 21;
    temperatures.push(new_temp);
    
    // Print the temperatures vector
    // Your code here
}

Hint

Use println!("{:?}", temperatures); to print the vector.

Practice

1. What does inserting an element at the end of an array mean in simple terms?

easy

A. Sorting the array in ascending order

B. Removing the first item from the array

C. Replacing the first item in the array

D. Adding a new item after the last existing item in the array

Solution

1. Step 1: Understand array structure

   An array is a list of items stored in order, starting from the first to the last.

2. Step 2: Define insertion at the end

   Inserting at the end means placing a new item right after the last item, extending the array by one.

3. Final Answer:

   Adding a new item after the last existing item in the array -> Option D

4. Quick Check:

   Insert at end = Add after last [OK]

Hint: Think: new item goes after the last one [OK]

Common Mistakes:

• Confusing insertion at end with removal
• Thinking insertion replaces an item
• Mixing insertion with sorting

2. Which Rust code snippet correctly inserts the value 10 at the end of a mutable vector named vec?

easy

A. vec.push(10);

B. vec.insert(0, 10);

C. vec[vec.len()] = 10;

D. vec.append(10);

Solution

1. Step 1: Identify correct method to add at end

   In Rust, push adds an element to the end of a vector.

2. Step 2: Check other options

   insert(0, 10) adds at start, vec[vec.len()] = 10 causes error (index out of bounds), append(10) is invalid syntax.

3. Final Answer:

   vec.push(10); -> Option A

4. Quick Check:

   Use push() to add at end [OK]

Hint: Use push() to add at the end of a vector [OK]

Common Mistakes:

• Using insert with wrong index
• Trying to assign to vec[vec.len()] directly
• Using append with a single value

3. What will be the output of this Rust code?

let mut numbers = vec![1, 2, 3];
numbers.push(4);
println!("{:?}", numbers);

medium

A. [1, 2, 3]

B. [4, 1, 2, 3]

C. [1, 2, 3, 4]

D. Compilation error

Solution

1. Step 1: Understand initial vector

   The vector numbers starts as [1, 2, 3].

2. Step 2: Apply push operation

   numbers.push(4) adds 4 at the end, making it [1, 2, 3, 4].

3. Final Answer:

   [1, 2, 3, 4] -> Option C

4. Quick Check:

   push(4) adds 4 at end [OK]

Hint: push() adds element at the end [OK]

Common Mistakes:

• Thinking push adds at start
• Expecting original vector unchanged
• Confusing output format

4. Identify the error in this Rust code that tries to insert 5 at the end of a vector:

let numbers = vec![1, 2, 3];
numbers.push(5);

medium

A. Cannot push because vector is immutable

B. push method does not exist for vectors

C. Syntax error in push call

D. No error, code runs fine

Solution

1. Step 1: Check vector mutability

   The vector numbers is declared without mut, so it is immutable.

2. Step 2: Understand push requirements

   push requires the vector to be mutable to add elements.

3. Final Answer:

   Cannot push because vector is immutable -> Option A

4. Quick Check:

   push needs mutable vector [OK]

Hint: Declare vector as mutable to push [OK]

Common Mistakes:

• Forgetting to add mut keyword
• Assuming push works on immutable vectors
• Misreading error as syntax problem

5. Given a vector vec with elements [2, 4, 6], write Rust code to insert the number 8 at the end and then remove the first element. What will be the final vector?

hard

A. [2, 4, 6, 8]

B. [4, 6, 8]

C. [8, 2, 4, 6]

D. [2, 4, 8]

Solution

1. Step 1: Insert 8 at the end

   Using vec.push(8), vector becomes [2, 4, 6, 8].

2. Step 2: Remove the first element

   Using vec.remove(0), removes 2, vector becomes [4, 6, 8].

3. Final Answer:

   [4, 6, 8] -> Option B

4. Quick Check:

   push then remove first = [4,6,8] [OK]

Hint: Push adds end, remove(0) deletes first [OK]

Common Mistakes:

• Removing last instead of first element
• Not updating vector after push
• Confusing remove index