How should I practice Trapping Rain Water?

Start by reading the full statement, solve the visible examples, then compare the pattern against related InMobi onsite interview problems in FastPrep.

Is Trapping Rain Water associated with InMobi?

FastPrep tags this as a InMobi onsite interview coding practice problem when the problem catalog has that company and stage context.

Problem · Array

Trapping Rain Water

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Problem statement

You are given an array heights, where heights[i] is the height of the ith bar in an elevation map. Every bar has width 1.

Return the total amount of rainwater that can be trapped between the bars.

Function

trapRainWater(heights: long[]) → long

Examples

Example 1

heights = [3,0,0,2,0,4]return = 10

The bars trap 3 + 3 + 1 + 3 = 10 units of water at indices 1, 2, 3, and 4.

Example 2

heights = [8,1,8,2,4]return = 9

The first basin traps 7 units above the bar of height 1, and the last basin traps 2 units above the bar of height 2.

Constraints

0 <= heights.length <= 10^6
0 <= heights[i] <= 10^9
The answer fits in a signed long.