42\. 接雨水
# 42. 接雨水 (opens new window)
# Description
Difficulty: 困难
Related Topics: 栈 (opens new window), 数组 (opens new window), 双指针 (opens new window), 动态规划 (opens new window), 单调栈 (opens new window)
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。
示例 1:
输入:height = [0,1,0,2,1,0,1,3,2,1,2,1]
输出:6
解释:上面是由数组 [0,1,0,2,1,0,1,3,2,1,2,1] 表示的高度图,在这种情况下,可以接 6 个单位的雨水(蓝色部分表示雨水)。
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示例 2:
输入:height = [4,2,0,3,2,5]
输出:9
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提示:
n == height.length
- 1 <= n <= 2 * 104
- 0 <= height[i] <= 105
# Solution
Language: JavaScript
/**
* @param {number[]} height
* @return {number}
*/
var trap = function(height) {
const n = height.length
const left = new Array(n).fill(0)
const right = new Array(n).fill(0)
let ans = 0
for (let i = 1; i < n; i++) {
left[i] = Math.max(left[i-1], height[i-1])
}
for (let i = n - 2; i >= 0; i--) {
right[i] = Math.max(right[i + 1], height[i + 1])
let short = Math.min(left[i], right[i]);
if (short > height[i]) {
ans += short - height[i]
}
}
return ans
};
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