Container With Most Water — Interview Guide

• Width × min(height[left], height[right]) is the candidate area.
• Moving the taller pointer can never increase the area (width shrinks and the limit is the shorter line).
• So always move the shorter pointer inward — the only moves that can improve the answer.

1. Place one pointer at each end.
2. Compute the area; track the maximum.
3. Move the pointer at the shorter line inward; repeat until they meet.

def max_area(h):
    l, r, best = 0, len(h) - 1, 0
    while l < r:
        best = max(best, (r - l) * min(h[l], h[r]))
        if h[l] < h[r]:
            l += 1
        else:
            r -= 1
    return best