---
title: '42. Trapping Rain Water'
description: 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
sidebar:
  label: 'Trapping Rain Water'
  badge: 'Hard'
---

<Badge variant="accent">Two Pointers</Badge>

### Example 1:
- Input: `height = [0,1,0,2,1,0,1,3,2,1,2,1]`
- Output: `6`
- Explanation: 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 * 10^4`
- `0 <= height[i] <= 10^5`

## Solution

```js
/**
 * @param {number[]} height
 * @return {number}
 */
var trap = function(height) {
    
};
```