The problem. You are given an array height where height[i] is the height of a vertical wall at position i. Pick two walls; together with the ground they form a container. Return the most water a container can hold. The water level stops at the shorter wall, so the amount is min(height[i], height[j]) × (j − i).
![Walls of heights [1, 8, 6, 2, 5, 4, 8, 3, 7]. The walls at index 1 (height 8) and index 8 (height 7) hold water up to height 7 across a width of 7, an area of 49.](/drawings/8eda09be-3daf-4e39-b1bd-7299553a8e75.svg)
Input: height = [1, 8, 6, 2, 5, 4, 8, 3, 7]
Output: 49 walls 1 and 8: min(8, 7) × (8 − 1) = 49
Input: height = [1, 1]
Output: 1Two forces pull against each other: width wants the walls far apart, and height wants both walls tall. Walls between the chosen two don't matter at all — they don't block the water.
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