Trapping Rain Water II
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
4After the rain, water is trapped between the blocks in two small ponds of 1 and 3 units, for a total volume of 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
10The surrounding boundary of height 3 traps water over the lower interior cells for a total volume of 10.
Constraints
- m == heightMap.length
- n == heightMap[i].length
- 1 <= m, n <= 200
- 0 <= heightMap[i][j] <= 2 * 10^4