407. Trapping Rain Water II LeetCode Solution | Easy Approach

Minimum Cost to Merge Stones

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: 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


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

Trapping Rain Water II Solutions

Time: O(n)
Space: O(n)


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