AlgoLounge

Trapping Rain Water

hard

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.

Examples

Example 1

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

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

Example 2

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

Constraints

  • n == height.length
  • 1 <= n <= 2 * 10⁴
  • 0 <= height[i] <= 10⁵
TypeScript
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List of test cases (10)
Case 1
height = [0,1,0,2,1,0,1,3,2,1,2,1]
Case 2
height = [4,2,0,3,2,5]
Case 3
height = [0,0,0]
Case 4
height = [3,0,2,0,4]
Case 5
height = [5,4,1,2]
Case 6
height = [2,1,2]
Case 7
height = [1,2,3,4,5]
Case 8
height = [5,4,3,2,1]
Case 9
height = [5,0,0,0,5]
Case 10
height = [0,2,0,2,0]