From ef40d69e2330de223c1bf8b53cf3e84abe9f278f Mon Sep 17 00:00:00 2001
From: Shyam-Chen <shyamchen1994@gmail.com>
Date: Sun, 14 Jul 2024 16:27:26 +0800
Subject: [PATCH] 164th Commit

---
 .../countHillValley.test.ts                   |  8 ++++
 .../countHillValley.ts                        | 39 +++++++++++++++++++
 2 files changed, 47 insertions(+)
 create mode 100644 src/page-20/2210. Count Hills and Valleys in an Array/countHillValley.test.ts
 create mode 100644 src/page-20/2210. Count Hills and Valleys in an Array/countHillValley.ts

diff --git a/src/page-20/2210. Count Hills and Valleys in an Array/countHillValley.test.ts b/src/page-20/2210. Count Hills and Valleys in an Array/countHillValley.test.ts
new file mode 100644
index 0000000..1a1546f
--- /dev/null
+++ b/src/page-20/2210. Count Hills and Valleys in an Array/countHillValley.test.ts	
@@ -0,0 +1,8 @@
+import { countHillValley } from './countHillValley';
+
+describe('2210. Count Hills and Valleys in an Array', () => {
+  test('countHillValley', () => {
+    expect(countHillValley([2, 4, 1, 1, 6, 5])).toBe(3);
+    expect(countHillValley([6, 6, 5, 5, 4, 1])).toBe(0);
+  });
+});
diff --git a/src/page-20/2210. Count Hills and Valleys in an Array/countHillValley.ts b/src/page-20/2210. Count Hills and Valleys in an Array/countHillValley.ts
new file mode 100644
index 0000000..c45c658
--- /dev/null
+++ b/src/page-20/2210. Count Hills and Valleys in an Array/countHillValley.ts	
@@ -0,0 +1,39 @@
+type CountHillValley = (nums: number[]) => number;
+
+/**
+ * Accepted
+ */
+export const countHillValley: CountHillValley = (nums) => {
+  let count = 0;
+
+  const n = nums.length;
+
+  for (let i = 1; i < n - 1; i++) {
+    // Skip if current element is the same as the previous one
+    if (nums[i] === nums[i - 1]) continue;
+
+    let left = i - 1;
+    let right = i + 1;
+
+    // Find the closest non-equal neighbor on the left
+    while (left >= 0 && nums[left] === nums[i]) {
+      left -= 1;
+    }
+
+    // Find the closest non-equal neighbor on the right
+    while (right < n && nums[right] === nums[i]) {
+      right += 1;
+    }
+
+    // Ensure that both left and right neighbors exist
+    if (left >= 0 && right < n) {
+      if (nums[i] > nums[left] && nums[i] > nums[right]) {
+        count += 1; // It's a hill
+      } else if (nums[i] < nums[left] && nums[i] < nums[right]) {
+        count += 1; // It's a valley
+      }
+    }
+  }
+
+  return count;
+};