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.
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.
class Solution:
def trap(self, height: List[int]) -> int:
ans = 0
leftHeight = self.leftMaxHeight(height)
rightHeight = self.rightMaxHeight(height)
for i in range(len(height)):
max_bar = min(leftHeight[i], rightHeight[i])
if max_bar > height[i]:
ans += max_bar - height[i]
return ans
def leftMaxHeight(self, height):
ans = [0] * len(height)
max_left = 0
for i in range(len(height)):
ans[i] = max_left
max_left = max(height[i], max_left)
return ans
def rightMaxHeight(self, height):
ans = [0] * len(height)
max_right = 0
for i in range(len(height)-1, -1, -1):
ans[i] = max_right
max_right = max(height[i], max_right)
return ans