力扣42 接雨水 （力扣11 盛最多水的容器 扩展）

// i 位置的左边最高柱子，要么左临元素的左边最高柱子，要么是他自己
// i 位置的右边最高柱子，要么右临元素的左边最高柱子，要么是他自己
lMax[i] = maxOf(lMax[i - 1], height[i])
rMax[i] = maxOf(rMax[i + 1], height[i])

class Solution {
    fun trap(height: IntArray): Int {
        val lMax = IntArray(height.size)
        val rMax = IntArray(height.size)
        lMax[0] = height[0]
        rMax[height.lastIndex] = height[height.lastIndex]
        var left:Int
        var right:Int
        for (i in 1..height.lastIndex) {
            left = i
            right = height.lastIndex - i
            lMax[left] = maxOf(lMax[left - 1], height[left])
            rMax[right] = maxOf(rMax[right + 1], height[right])
        }
        var count = 0
        for (i in height.indices) {
            count += (minOf(rMax[i], lMax[i]) - height[i])
            println(count)
        }
    }
}

class Solution {
    fun trap(height: IntArray): Int {
        if (height.size <= 2) {
            return 0
        }
        var lM = 0
        var rM = 0
        var left = 0
        var right = height.lastIndex
        var count = 0
        while (left < right) {
            lM = maxOf(lM, height[left])
            rM = maxOf(rM, height[right])
            if (lM < rM) {
                count += lM - height[left]
                left++
            } else {
                count += rM - height[right]
                right--
            }
        }
        return count
    }
}