feat: implement unsorted subarray algorithm

Author: francislagares

src/algorithms/unsorted-subarray/tests/unsorted-subarray.test.ts

@@ -0,0 +1,27 @@
+import { findUnsortedSubarray } from '../unsorted-subarray';
+
+describe('findUnsortedSubarray', () => {
+  test('should return 0 for already sorted array', () => {
+    expect(findUnsortedSubarray([1, 2, 3, 4, 5])).toBe(0);
+  });
+
+  test('should return 0 for empty array', () => {
+    expect(findUnsortedSubarray([])).toBe(0);
+  });
+
+  test('should return 0 for single element array', () => {
+    expect(findUnsortedSubarray([1])).toBe(0);
+  });
+
+  test('should return correct length for partially unsorted array', () => {
+    expect(findUnsortedSubarray([1, 3, 2, 0, 5])).toBe(4);
+  });
+
+  test('should return array length for completely unsorted array', () => {
+    expect(findUnsortedSubarray([5, 4, 3, 2, 1])).toBe(5);
+  });
+
+  test('should handle array requiring boundary extension', () => {
+    expect(findUnsortedSubarray([1, 3, 5, 2, 6, 4, 7])).toBe(5);
+  });
+});

src/algorithms/unsorted-subarray/unsorted-subarray.ts

@@ -0,0 +1,41 @@
+export const findUnsortedSubarray = (nums: number[]): number => {
+  if (nums.length <= 1) return 0;
+
+  let left = 0;
+  let right = nums.length - 1;
+
+  // Find left boundary
+  while (left < nums.length - 1 && nums[left] <= nums[left + 1]) {
+    left++;
+  }
+
+  // Find right boundary
+  while (right > 0 && nums[right] >= nums[right - 1]) {
+    right--;
+  }
+  // Array is already sorted
+  if (left === nums.length - 1) return 0;
+
+  // Step 3: Find min and max in the subarray
+  let subarrayMin = Number.MAX_VALUE;
+  let subarrayMax = Number.MIN_VALUE;
+
+  for (let i = left; i <= right; i++) {
+    subarrayMin = Math.min(subarrayMin, nums[i]);
+    subarrayMax = Math.max(subarrayMax, nums[i]);
+  }
+
+  // Step 4: Extend boundaries if needed
+  while (left > 0 && nums[left - 1] > subarrayMin) {
+    left--;
+  }
+  while (right < nums.length - 1 && nums[right + 1] < subarrayMax) {
+    right++;
+  }
+
+  // Step 5: Return length
+  return right - left + 1;
+};
+
+console.log(findUnsortedSubarray([1, 3, 2, 0, 5])); // Output: 4
+console.log(findUnsortedSubarray([1, 2, 3, 4])); // Output: 0