leedcode:接雨水(单调栈)

4.4日：接雨水

给定n个非负整数表示每个宽度为1的柱子的高度图，计算按此排列的柱子，下雨之后能接多少雨水。

1. 找出最高点
2. 分别从两边往最高点遍历：如果下一个数比当前数小，说明可以接到水

class Solution(object):
    def trap(self, height):
        """
        :type height: List[int]
        :rtype: int
        """
        if len(height) <= 1:
            return 0
        
        max_height = 0
        max_height_index = 0
        
        # 找到最高点
        for i in range(len(height)):
            h = height[i]
            if h > max_height:
                max_height = h
                max_height_index = i
        
        area = 0
        
        # 从左边往最高点遍历
        tmp = height[0]
        for i in range(max_height_index):
            if height[i] > tmp:
                tmp = height[i]
            else:
                area = area + (tmp - height[i])
        
        # 从右边往最高点遍历
        tmp = height[-1]
        for i in reversed(range(max_height_index + 1, len(height))):
            if height[i] > tmp:
                tmp = height[i]
            else:
                area = area + (tmp - height[i])
        
        return area