164th Commit

src/page-20/2210. Count Hills and Valleys in an Array/countHillValley.test.ts

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+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);
+  });
+});

src/page-20/2210. Count Hills and Valleys in an Array/countHillValley.ts

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+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;
+};