leetcode

Trapping Rain Water

Trapping Rain Water

O(1) Version - 44ms

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class Solution:
    def trap(self, height):
        """
        :type height: List[int]
        :rtype: int
        """
        left = right = water = 0
        i, j = 0, len(height) - 1
        while i <= j:
            left, right = max(left, height[i]), max(right, height[j])
            while i <= j and height[i] <= left <= right:
                water += left - height[i]
                i += 1
            while i <= j and height[j] <= right <= left:
                water += right - height[j]
                j -= 1
        return water

test code

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In [36]: s = Solution(); t = s.trap([0,1,0,2,1,0,1,3,2,1,2,1])
In [37]: t
Out[37]: 6

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