Add Tournament Sort implementation

Author: DANIEL DRORI

Sorts/TournamentSort.js

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+/*
+ * Tournament Sort
+ *
+ * Tournament Sort improves upon naive Selection Sort by using a min-heap
+ * (priority queue) to find the minimum element in O(log n) instead of O(n),
+ * giving an overall time complexity of O(n log n).
+ *
+ * The name comes from its resemblance to a single-elimination sports tournament
+ * where the winner (minimum element) is found each round.
+ *
+ * Reference: https://en.wikipedia.org/wiki/Tournament_sort
+ */
+
+/**
+ * Restores the min-heap property by sifting down from index i.
+ * @param {number[]} heap - The heap array
+ * @param {number} n - Size of the heap
+ * @param {number} i - Index to sift down from
+ */
+const heapify = (heap, n, i) => {
+  let smallest = i
+  const left = 2 * i + 1
+  const right = 2 * i + 2
+
+  if (left < n && heap[left] < heap[smallest]) smallest = left
+  if (right < n && heap[right] < heap[smallest]) smallest = right
+
+  if (smallest !== i) {
+    ;[heap[i], heap[smallest]] = [heap[smallest], heap[i]]
+    heapify(heap, n, smallest)
+  }
+}
+
+/**
+ * Sorts an array using Tournament Sort.
+ * @param {number[]} arr - The array to sort
+ * @returns {number[]} The sorted array
+ */
+const tournamentSort = (arr) => {
+  if (arr.length <= 1) return arr
+
+  const heap = [...arr]
+  const result = []
+
+  // Build min-heap
+  for (let i = Math.floor(heap.length / 2) - 1; i >= 0; i--) {
+    heapify(heap, heap.length, i)
+  }
+
+  // Extract minimum elements one by one
+  let size = heap.length
+  while (size > 0) {
+    result.push(heap[0])
+    heap[0] = heap[size - 1]
+    size--
+    heapify(heap, size, 0)
+  }
+
+  return result
+}
+
+export { tournamentSort }

Sorts/TournamentSort.test.js

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+import { tournamentSort } from './TournamentSort.js'
+
+describe('Tournament Sort', () => {
+  it('should sort an unsorted array', () => {
+    expect(tournamentSort([5, 3, 1, 4, 2])).toEqual([1, 2, 3, 4, 5])
+  })
+
+  it('should handle an already sorted array', () => {
+    expect(tournamentSort([1, 2, 3, 4, 5])).toEqual([1, 2, 3, 4, 5])
+  })
+
+  it('should handle a reverse sorted array', () => {
+    expect(tournamentSort([5, 4, 3, 2, 1])).toEqual([1, 2, 3, 4, 5])
+  })
+
+  it('should handle a single element array', () => {
+    expect(tournamentSort([42])).toEqual([42])
+  })
+
+  it('should handle an empty array', () => {
+    expect(tournamentSort([])).toEqual([])
+  })
+
+  it('should handle duplicates', () => {
+    expect(tournamentSort([3, 1, 2, 1, 3])).toEqual([1, 1, 2, 3, 3])
+  })
+
+  it('should handle negative numbers', () => {
+    expect(tournamentSort([-3, 0, -1, 5, 2])).toEqual([-3, -1, 0, 2, 5])
+  })
+})