[leetcode] Trapping rain water

標籤：

42. 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.

For example, 
Given [0,1,0,2,1,0,1,3,2,1,2,1], return 6.

 

Solution:

Sum water amount of each bin (width=1). Maintain a height of left and right seperately, which is like a one-side wall of partial container. Fix the higher one and add the water amount regard to the lower part. 

 

class Solution(object):    def trap(self, height):        """        :type height: List[int]        :rtype: int        """        left, right = 0, 0        start, end = 0, len(height)-1        result = 0        while start <= end:            if left<right:                if height[start]>=left:                    left = height[start]                else:                    result += left - height[start]                start += 1            else:                if height[end]>=right:                    right = height[end]                else:                    result += right - height[end]                end -= 1        return result

 

[leetcode] Trapping rain water