Total Rainwater Trapped Across an Elevation Map
Implement totalRainwaterTrapped
You're given an array
height where each value is the height of a unit-width bar standing at that position. After it rains, water settles in the dips between bars — compute the total volume of water trapped across the whole map.
Try to avoid two extra O(n) arrays for the left/right running maximums — a two-pointer sweep from both ends can get you there in O(1) extra space.
Example 1:
Input: height = [2,0,3,0,4,0,1]
Output: 6
Example 2:
Input: height = [4,1,3,1,5,2]
Output: 7
Example 3:
Input: height = [1,0,2]
Output: 1
+ 5 hidden test cases run on Submit.
Constraints:
- ●
1 ≤ height.length ≤ 2 × 10⁴ - ●
0 ≤ height[i] ≤ 10⁵
height =
[2, 0, 3, 0, 4, 0, 1]