trapping-rain-water

 https://leetcode.com/problems/trapping-rain-water/

brute-force 

water at any x = min( max_left_of_x, max_right_of_x) - height_of_x

two-pointer solution 

when keeping 

1) 

• p_start, at 0
• p_end at 11 [length-1] of array
• check, 
• p_start height is less. => 0
  
• p_end height is less => 1
  
• answer: p_start => 0 is lesser
  

• height at 0 is less
• p_start becomes our p_current pointer.
• with respect to p_current
• we check 
• max_left
• max_right  

1. whenever we check which is lesser p_start, p_end, we are actually evaluating  min(p_start, p_end)
2. by checking min, of two, we get the level, which water can be filled.

formula

 

Level => check min of p_start, p_end 

current_level = min(p_start, p_end)

if p_start is less, we start from left, and 

• make max_left = height_at_p_start 
• make max_right = height_at_p_end
• we consider level = max_left 
•  
  

***incomplete post