Given n non-negative integers representing an elevation map where the width of each bar is 1, compute how much water it is able to trap after raining.
Input Format
The only argument given is integer array A.
Output Format
Return the total water it is able to trap after raining.
Example
Input 1:
A = [0,1,0,2,1,0,1,3,2,1,2,1]
Output 1:
6
Explaination 1:
In this case, 6 units of rain water (blue section) are being trapped.
NOTE: You only need to implement the given function.
Do not read input, instead use the arguments to the function.
Do not print the output, instead return values as specified.