Recall & Review
beginner
What is the main goal of the Trapping Rain Water Problem?
To find how much water can be trapped between bars of different heights after raining.
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beginner
What does the 'left max' array represent in the Trapping Rain Water Problem?
It stores the highest bar height from the left up to each position.
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intermediate
Why do we need both 'left max' and 'right max' arrays?
Because water trapped at each bar depends on the tallest bars on both left and right sides.
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beginner
How is the water trapped at a single bar calculated?
Water trapped = minimum of (left max, right max) - height of the bar, if positive.
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intermediate
What is the time complexity of the standard solution using left max and right max arrays?
O(n), where n is the number of bars, because we traverse the array a few times linearly.
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What does the Trapping Rain Water Problem calculate?
✗ Incorrect
The problem calculates how much water can be trapped between bars after raining.
Which arrays are used to store the highest bars from left and right?
✗ Incorrect
We use left max and right max arrays to store the tallest bars from left and right sides.
How do you calculate water trapped at a bar?
✗ Incorrect
Water trapped is the minimum of left max and right max minus the bar's height.
What is the time complexity of the standard trapping rain water solution?
✗ Incorrect
The solution runs in linear time O(n) by traversing the array multiple times.
If a bar is the tallest on both sides, how much water can it trap?
✗ Incorrect
A tallest bar cannot trap water on top of itself, so trapped water is zero.
Explain how to calculate the total trapped rain water given an array of bar heights.
Think about the tallest bars on both sides of each bar.
You got /4 concepts.
Describe the role of the left max and right max arrays in the Trapping Rain Water Problem.
They help find the boundaries for water trapping.
You got /3 concepts.