Array Deletion at End in DSA Typescript - Practice Problems & Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output after deleting the last element?

Consider the following TypeScript code that deletes the last element from an array. What will be the printed output?

DSA Typescript

const arr = [10, 20, 30, 40, 50];
arr.pop();
console.log(arr);

A []

B [10, 20, 30, 40, 50]

C [20, 30, 40, 50]

D [10, 20, 30, 40]

💡 Hint

The pop() method removes the last element from the array.

The pop() method removes the last element (50) from the array, so the remaining elements are [10, 20, 30, 40].

❓ Predict Output

intermediate

What happens if pop() is called on an empty array?

What will be the output of the following TypeScript code?

DSA Typescript

const arr: number[] = [];
const removed = arr.pop();
console.log(removed);
console.log(arr);

A

null
[]

B

undefined
[]

C

0
[]

D

Error
[]

💡 Hint

pop() returns undefined if the array is empty.

Calling pop() on an empty array returns undefined and the array remains empty.

🔧 Debug

advanced

Why does this code throw an error when deleting the last element?

Identify the error in the following TypeScript code that tries to delete the last element from an array.

DSA Typescript

const arr = [1, 2, 3];
arr.pop;
console.log(arr);

A pop throws a runtime error

B pop method does not exist on array

C pop is not called as a function, so no element is removed

D pop removes the first element instead of last

💡 Hint

Check if pop is called with parentheses.

pop is a function and must be called with parentheses (). Without them, the method is not executed and the array remains unchanged.

❓ Predict Output

advanced

What is the array after multiple deletions at the end?

What will be the output after executing the following code?

DSA Typescript

const arr = [5, 10, 15, 20, 25];
arr.pop();
arr.pop();
console.log(arr);

A [5, 10, 15]

B [5, 10, 15, 20]

C [10, 15, 20, 25]

D [5, 10]

💡 Hint

Each pop removes one element from the end.

Two pop() calls remove 25 and then 20, leaving [5, 10, 15].

🧠 Conceptual

expert

What is the time complexity of deleting the last element from an array?

In most programming languages including TypeScript, what is the time complexity of deleting the last element from a dynamic array using pop()?

A O(1) - Constant time

B O(n^2) - Quadratic time

C O(log n) - Logarithmic time

D O(n) - Linear time

💡 Hint

Consider how pop() works internally on dynamic arrays.

Deleting the last element with pop() is a constant time operation because it just removes the last item without shifting others.

Practice

1. What does the pop() method do when called on an array in TypeScript?

easy

A. Removes the last element from the array and returns it

B. Removes the first element from the array and returns it

C. Adds a new element to the end of the array

D. Returns the length of the array without changing it

Solution

1. Step 1: Understand the pop() method

   The pop() method removes the last element from an array and returns that element.

2. Step 2: Compare with other options

   Other options describe different methods: removing first element is shift(), adding element is push(), and returning length is length property.

3. Final Answer:

   Removes the last element from the array and returns it -> Option A

4. Quick Check:

   pop() removes last element = A [OK]

Hint: pop() always removes from the end of the array [OK]

Common Mistakes:

• Confusing pop() with shift()
• Thinking pop() adds elements
• Assuming pop() returns array length

2. Which of the following is the correct syntax to remove the last element from an array named numbers in TypeScript?

easy

A. numbers.removeLast();

B. numbers.deleteEnd();

C. pop(numbers);

D. numbers.pop();

Solution

1. Step 1: Recall the correct method to remove last element

   The correct method is pop() called on the array object.

2. Step 2: Check syntax correctness

   Only numbers.pop(); is valid TypeScript syntax. Other options are not valid methods or functions.

3. Final Answer:

   numbers.pop(); -> Option D

4. Quick Check:

   Correct pop() syntax = B [OK]

Hint: Use arrayName.pop() to remove last element [OK]

Common Mistakes:

• Using non-existent methods like removeLast()
• Calling pop() as a standalone function
• Using incorrect method names

3. What will be the output of the following TypeScript code?

let fruits = ['apple', 'banana', 'cherry'];
let removed = fruits.pop();
console.log(fruits);
console.log(removed);

medium

A. ['apple', 'banana', 'cherry'] and 'cherry'

B. ['apple', 'banana', 'cherry'] and undefined

C. ['apple', 'banana'] and 'cherry'

D. ['apple', 'banana'] and 'banana'

Solution

1. Step 1: Understand pop() effect on array

   Calling pop() removes the last element 'cherry' from fruits and returns it.

2. Step 2: Trace the console.log outputs

   After pop, fruits is ['apple', 'banana'] and removed is 'cherry'.

3. Final Answer:

   ['apple', 'banana'] and 'cherry' -> Option C

4. Quick Check:

   pop() removes last element = D [OK]

Hint: pop() returns removed last element and shortens array [OK]

Common Mistakes:

• Expecting pop() to remove first element
• Thinking pop() returns the new array
• Confusing removed element with array length

4. Identify the error in the following TypeScript code that tries to remove the last element from an array items:

let items = [10, 20, 30];
items.pop;
console.log(items);

medium

A. Missing parentheses after pop method call

B. pop method does not exist on arrays

C. pop should be called as a standalone function

D. pop removes the first element, not last

Solution

1. Step 1: Check method call syntax

   The code uses items.pop; without parentheses, so the method is not called.

2. Step 2: Understand consequences

   Without parentheses, pop is just a reference, so the array remains unchanged.

3. Final Answer:

   Missing parentheses after pop method call -> Option A

4. Quick Check:

   pop() needs () to execute = A [OK]

Hint: Always use () to call methods like pop() [OK]

Common Mistakes:

• Forgetting parentheses on method calls
• Thinking pop is a standalone function
• Confusing pop with shift

5. Given the array let nums = [5, 10, 15, 20];, which code snippet correctly removes the last two elements and returns the modified array?

hard

A. nums.pop(2); return nums;

B. nums.pop(); nums.pop(); return nums;

C. nums.splice(-2, 1); return nums;

D. nums.removeLast(2); return nums;

Solution

1. Step 1: Understand pop() removes one element at a time

   Calling pop() twice removes last two elements one by one.

2. Step 2: Check other options

   splice(-2, 1) removes only one element. pop(2) and removeLast(2) are invalid methods.

3. Final Answer:

   nums.pop(); nums.pop(); return nums; -> Option B

4. Quick Check:

   pop() removes one element; call twice for two [OK]

Hint: Call pop() twice to remove two elements from end [OK]

Common Mistakes:

• Trying pop() with arguments
• Using splice with incorrect parameters
• Using non-existent methods like removeLast