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TODO 0042. Trapping Rain Water   hard

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.

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}

TODO Approach

Write your approach here.

TODO Python

class Solution:
    def trap(self, height: List[int]) -> int:

TODO C++

class Solution {
public:
    int trap(vector<int>& height) {
        
    }
};