返回题库

接雨水

Trapping Rain Water

专题
Algorithmic Programming / 算法编程
难度
L4
来源
Citadel

题目详情

问题：接雨水

考察：数组、双指针、动态规划

来源：Citadel

链接：https://www.jointaro.com/interviews/questions/trapping-rain-water/

Given n non-negative integers representing an elevation map where the width of each bar is 1, compute how much water it can trap after raining.

 

Example 1:

Input: height = [0,1,0,2,1,0,1,3,2,1,2,1]
Output: 6
Explanation: The above elevation map (black section) is represented by array [0,1,0,2,1,0,1,3,2,1,2,1]. In this case, 6 units of rain water (blue section) are being trapped.

Example 2:

Input: height = [4,2,0,3,2,5]
Output: 9

 

Constraints:

  • n == height.length
  • 1 <= n <= 2 * 104
  • 0 <= height[i] <= 105
解析

思路：用左右双指针维护两侧最高柱。较低的一侧决定当前位置能接多少水，移动较低侧并用对应最大高度更新答案。

复杂度：时间 O(n)，空间 O(1)。