Binary Search on Answer Technique in DSA Typescript - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the main idea behind the Binary Search on Answer Technique?

It is a method to find an unknown value by guessing an answer range and using binary search to narrow down the correct answer based on a condition check.

beginner

In Binary Search on Answer, what does the 'answer' represent?

The 'answer' is the value we want to find, often a number or limit, which satisfies a given condition or constraint in the problem.

intermediate

Why do we use binary search on the answer instead of directly searching the input data?

Because the answer lies within a range and checking if a guess is valid is easier than searching the entire input; this reduces time complexity by focusing on the answer space.

intermediate

What is a key requirement for applying Binary Search on Answer Technique?

The problem must have a monotonic condition: if a guess is valid, then all guesses greater (or smaller) than it are also valid or invalid, allowing binary search to work.

beginner

How do you check if a guessed answer is valid in Binary Search on Answer?

You write a function that tests the guess against the problem's constraints and returns true if the guess meets the conditions, false otherwise.

What does the 'answer' in Binary Search on Answer Technique usually represent?

A An element in the input array

B The middle index of the array

C A value within a range that satisfies a condition

D The maximum value in the input

The answer is a value we guess and test to find if it satisfies the problem's condition.

What is essential for the condition checked during Binary Search on Answer?

A It must be non-deterministic

B It must be random

C It must be always false

D It must be monotonic (always true or false beyond a point)

Monotonicity ensures binary search can correctly narrow down the answer.

Which of these is NOT a step in Binary Search on Answer Technique?

A Sort the input array

B Check if guess is valid

C Guess an answer in the range

D Adjust range based on validity

Sorting input is not always required; the technique focuses on searching the answer space.

If a guess is valid in Binary Search on Answer, what can we say about guesses smaller than it in a monotonic problem?

A They are also valid

B They are invalid

C They might be valid or invalid

D They are always equal

In monotonic problems, if a guess is valid, smaller guesses are invalid or vice versa depending on problem.

What is the time complexity benefit of using Binary Search on Answer?

A Reduces search from linear to logarithmic in answer range

B Increases time complexity

C No change in time complexity

D Depends on input size only

Binary search reduces the number of guesses needed by half each time, making it efficient.

Explain the Binary Search on Answer Technique and when it is useful.

Think about searching for a number by checking if it fits a rule.

Describe how to implement a validity check function in Binary Search on Answer.

This function decides if the guessed answer is good or not.