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Commit 3b0be0a

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Merge pull request TheAlgorithms#527 from kgolder92/add-trapping-water
complete trapping rain water
2 parents d272b1e + d70595e commit 3b0be0a

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/**
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* @param {number[]} height
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* @return {number}
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*/
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/* 42. Trapping Rain Water
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https://leetcode.com/problems/trapping-rain-water/
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Helpful animation of this prompt: https://youtu.be/HmBbcDiJapY?t=51
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Given n non-negative integers representing an elevation map where
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the width of each bar is 1, compute how much water it is able to trap
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after raining.
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VIEW ELEVATION MAP ON LEETCODE
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Example:
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Input: [0,1,0,2,1,0,1,3,2,1,2,1]
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Output: 6
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Plan:
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iterate through and find left maxes
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iterate through and find right maxes
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create minheight and assign it to the min(leftmax, rightmax)
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if current height(element) < minheight
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push minheight - height into water array
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else
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push 0 onto water array
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sum up water array and return
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left maxes = [0,0,1,1,2,2,2,2,3,3,3,3]
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right maxes = [3,3,3,3,3,3,3,2,2,2,1,0]
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water contained = [0,0,1,0,1,2,1,0,0,1,0,0] -> sum = 6
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*/
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function trap (heights) {
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const maxes = new Array(heights.length).fill(0)
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let leftMax = 0
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for (let i = 0; i < heights.length; i++) {
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const height = heights[i]
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maxes[i] = leftMax
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leftMax = Math.max(leftMax, height)
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}
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let rightMax = 0
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for (let i = heights.length - 1; i >= 0; i -= 1) {
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const height = heights[i]
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const minHeight = Math.min(rightMax, maxes[i])
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if (height < minHeight) {
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maxes[i] = minHeight - height
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} else {
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maxes[i] = 0
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}
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rightMax = Math.max(rightMax, height)
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}
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return maxes.reduce((a, b) => a + b, 0)
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}
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console.log(trap([0, 1, 0, 2, 1, 0, 1, 3, 2, 1, 2, 1])) // -> 6

‎package-lock.json‎

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‎package.json‎

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"jest": "^26.4.2",
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"standard": "^14.3.4"
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}
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}
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}

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