Rainwater Trapping

Function Name: trapRainwater

Description

Write a function called trapRainwater that calculates how much rainwater can be trapped between the given heights of bars. You are given an array that represents an elevation map where the width of each bar is 1. The function should compute how much water is trapped after raining. Bars of width 1 and non-negative integers are represented in the array where each value represents the height of the bar at that position.

Requirements

• The function should take an array of integers as its parameter.
• You should not use any built-in functions that directly solve the problem, like third-party algorithm implementations.
• Optimize the function for time complexity where possible.
• Write clean and readable code with proper variable names and comments.
• Do not mutate the original array.
• Handle the edge case where the input array is empty, in which case the function should return 0.
• Assume the input array's length does not exceed 10,000 elements.

Examples

trapRainwater([0,1,0,2,1,0,1,3,2,1,2,1]) should return 6.trapRainwater([4,2,0,3,2,5]) should return 9.trapRainwater([]) should return 0.

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