Trapping Rain Water II

Hard

Given an m x n matrix of non-negative integers representing the height of each cell, return the volume of water that can be trapped 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

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*10^4.