Container With Most Water

mediumTests passed 2026-11-11v1.0.0

TC: O(N)|SC: O(1)

Two Pointers Original Statement (leetcode).md

1. Core Invariant / The Trick

Start with widest container `(l=0, r=n-1)`. Always move the SHORTER wall inward: advancing the taller wall can only shrink width while keeping height bounded by the untouched shorter wall.

2. Complexity Bounds & Proof

Greedy exchange proof: no pair using the shorter wall with a narrower width can beat the current width.

3. Minimal Idiomatic Code

def maxArea(height: list[int]) -> int:
    l, r = 0, len(height) - 1
    best = 0
    while l < r:
        best = max(best, (r - l) * min(height[l], height[r]))
        if height[l] < height[r]: l += 1
        else: r -= 1
    return best

4. Failure Modes & Interview Follow-ups

Pitfalls:- Confusing with Trapping Rain Water (this looks at pair extremes only, no bar obstruction subtraction).

Follow-ups:- Trapping Rain Water calculates cumulative depth across every index.

Personal Notes & Scratchpad (Local-First Yjs CRDT)

Saved instantaneously in IndexedDB. Streams live across peers via Hocuspocus when signed in.

Related Invariants

Trapping Rain Water (O(N))

Browser Scratchpad

Console Output

Click Run or press Cmd/Ctrl+Enter to execute locally in a Web Worker.