Container With Most Water in DSA C - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the 'Container With Most Water' problem ask you to find?

It asks to find two lines in an array that, together with the x-axis, form a container that holds the maximum amount of water.

beginner

What is the main idea behind the two-pointer approach for this problem?

Use two pointers at the start and end of the array, calculate area, then move the pointer with the smaller height inward to try to find a bigger container.

intermediate

Why do we move the pointer with the smaller height in the two-pointer method?

Because the area is limited by the smaller height, moving it might find a taller line and increase the area.

intermediate

What is the time complexity of the optimal solution for 'Container With Most Water'?

O(n), where n is the number of lines, because each pointer moves at most n times.

intermediate

What would be the output for the input heights [1,8,6,2,5,4,8,3,7]?

The maximum area is 49, formed between lines at index 1 (height 8) and index 8 (height 7).

In the two-pointer approach, where do the pointers start?

A In the middle of the array

B Both at the beginning

C At the beginning and end of the array

D Both at the end

The two pointers start at the beginning and end to check the widest container first.

What limits the amount of water a container can hold?

A The shorter line

B The taller line

C The distance between lines only

D The sum of both lines' heights

The container's height is limited by the shorter line because water cannot go above it.

What happens if you move the pointer pointing to the taller line inward?

A Area might increase

B Area might decrease or stay the same

C Area always increases

D Area always decreases

Moving the taller line pointer inward might reduce width without increasing height, so area might decrease or stay the same.

What is the time complexity of the brute force solution?

A O(n^2)

B O(n)

C O(n log n)

D O(log n)

Brute force checks all pairs, which takes O(n^2) time.

Which of these is a correct step in the two-pointer algorithm?

A Move pointers randomly

B Always move the pointer with the taller line

C Move both pointers inward simultaneously

D Always move the pointer with the shorter line

Moving the pointer with the shorter line can potentially find a taller line and increase area.

Explain the two-pointer approach to solve the 'Container With Most Water' problem.

Think about how to maximize area by adjusting pointers.

Describe why the area is limited by the shorter line in the container problem.

Imagine water filling between two walls of different heights.