Feat | NeetCode | Roadmap | #14 Trapping Rain Water

README.md

@@ -83,4 +83,5 @@
   - [Task #10](src/neetcode/two-pointers/valid-palindrome) - _Valid Palindrome_ - _[check the task](https://neetcode.io/problems/is-palindrome)_
   - [Task #11](src/neetcode/two-pointers/two-sum-ii-input-array-is-sorted) - _Two Sum II Input Array Is Sorted_ - _[check the task](https://neetcode.io/problems/two-integer-sum-ii)_
   - [Task #12](src/neetcode/two-pointers/3sum) - _3Sum_ - _[check the task](https://neetcode.io/problems/three-integer-sum)_
-  - [Task #13](src/neetcode/two-pointers/container-with-most-water) - _Container With Most Water_ - _[check the task](https://neetcode.io/problems/max-water-container)_
+  - [Task #13](src/neetcode/two-pointers/container-with-most-water) - _Container With Most Water_ - _[check the task](https://neetcode.io/problems/max-water-container)_
+  - [Task #14](src/neetcode/two-pointers/trapping-rain-water) - _Trapping Rain Water_ - _[check the task](https://neetcode.io/problems/trapping-rain-water)_

src/neetcode/two-pointers/trapping-rain-water/solution.test.ts

@@ -0,0 +1,8 @@
+import { trap } from './solution';
+
+describe('Trapping Rain Water | NeetCode | RoadMap | Testcases', () => {
+  test('#1', () => {
+    const height = [0, 2, 0, 3, 1, 0, 1, 3, 2, 1];
+    expect(trap(height)).toBe(9);
+  });
+});

src/neetcode/two-pointers/trapping-rain-water/solution.ts

@@ -0,0 +1,30 @@
+/**
+ * @param {number[]} height - an array of non-negative integers which represent an elevation map.
+ * Each value `height[i]` represents the height of a bar, which has a width of `1`.
+ * @return {number} - the maximum area of water that can be trapped between the bars.
+ */
+export const trap = (height: number[]): number => {
+  if (height.length === 0) {
+    return 0;
+  }
+
+  let l = 0;
+  let r = height.length - 1;
+  let lMax = height[l];
+  let rMax = height[r];
+  let res = 0;
+
+  while (l < r) {
+    if (lMax < rMax) {
+      l++;
+      lMax = Math.max(lMax, height[l]);
+      res += lMax - height[l];
+    } else {
+      r--;
+      rMax = Math.max(rMax, height[r]);
+      res += rMax - height[r];
+    }
+  }
+
+  return res;
+};