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Trapping Rain Water

Hard

Two Pointers

Given n non-negative integers representing an elevation map where the width of each bar is 1, compute how much water it can trap after raining.

Example 1

Input:height = [0,1,0,2,1,0,1,3,2,1,2,1]
Output:6

The elevation map is represented by array [0,1,0,2,1,0,1,3,2,1,2,1]. In this case, 6 units of rain water are being trapped.

Example 2

Input:height = [4,2,0,3,2,5]
Output:9

Adding trapped water at each index in this elevation map gives a total of 9.

Constraints

  • n == height.length
  • 1 <= n <= 2 * 104
  • 0 <= height[i] <= 105
solution.js
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Test Cases (2)

Test Case 1
Input:
[0,1,0,2,1,0,1,3,2,1,2,1]
Expected Output:
6
Test Case 2
Input:
[4,2,0,3,2,5]
Expected Output:
9