Solution (leetcode-in-java 1.21 API)

java.lang.Object
- g0401_0500.s0407_trapping_rain_water_ii.Solution

```
public class Solution
extends Object
```
407 - Trapping Rain Water II.
Hard

Given an m x n integer matrix heightMap representing the height of each unit cell in a 2D elevation map, return the volume of water it can trap after raining.

Example 1:

Input: heightMap = [[1,4,3,1,3,2],[3,2,1,3,2,4],[2,3,3,2,3,1]]

Output: 4

Explanation:
```
 After the rain, water is trapped between the blocks.
 We have two small ponds 1 and 3 units trapped.
 The total volume of water trapped is 4. 
```
Example 2:

Input: heightMap = [[3,3,3,3,3],[3,2,2,2,3],[3,2,1,2,3],[3,2,2,2,3],[3,3,3,3,3]]

Output: 10

Constraints:
- m == heightMap.length
- n == heightMap[i].length
- 1 <= m, n <= 200
- 0 <= heightMap[i][j] <= 2 * 10⁴

- Constructor Summary
  
  Constructors
  Constructor Description
  
  Solution()
- Method Summary
  
  All Methods Instance Methods Concrete Methods
  Modifier and Type Method Description
  
  int trapRainWater(int[][] heightMap)
  - Methods inherited from class java.lang.Object
    clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail
- Solution
```
public Solution()
```

Method Detail

trapRainWater

public int trapRainWater(int[][] heightMap)