Coding - Trapping Rain Water

Problem Statement

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.

Examples

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
• 0 <= n <= 3 * 10^4
• 0 <= height[i] <= 10^5

Hints

1. Two-pointer technique can be used to solve this problem efficiently.
2. Keep track of the maximum height seen so far on the left and right sides.
3. Calculate the trapped water by comparing the current height with the maximum heights on both sides.