Add Tournament Sort implementation

sorting/tournament_sort.cpp

@@ -0,0 +1,109 @@
+/**
+ * @file tournament_sort.cpp
+ * @brief Implementation of [Tournament Sort]
+ * (https://en.wikipedia.org/wiki/Tournament_sort)
+ *
+ * @details
+ * Tournament Sort is a sorting algorithm that improves upon naive selection
+ * sort by using a min-heap (priority queue) to find the next minimum element.
+ *
+ * Instead of scanning all n elements each round (O(n)), a heap finds the
+ * minimum in O(log 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.
+ *
+ * Time Complexity: O(n log n)
+ * Space Complexity: O(n)
+ *
+ * @author drori12
+ */
+
+#include <algorithm>   /// for std::is_sorted
+#include <cassert>     /// for assert
+#include <iostream>    /// for std::cout
+#include <queue>       /// for std::priority_queue
+#include <vector>      /// for std::vector
+
+/**
+ * @namespace sorting
+ * @brief Sorting algorithms
+ */
+namespace sorting {
+
+/**
+ * @brief Tournament sort using a min-heap priority queue.
+ * @tparam T type of elements in the array (must support < operator)
+ * @param arr input vector to be sorted
+ * @return sorted vector in ascending order
+ */
+template <typename T>
+std::vector<T> tournament_sort(std::vector<T> arr) {
+    // min-heap: smallest element always on top
+    std::priority_queue<T, std::vector<T>, std::greater<T>> min_heap(
+        arr.begin(), arr.end());
+
+    std::vector<T> sorted;
+    sorted.reserve(arr.size());
+
+    while (!min_heap.empty()) {
+        sorted.push_back(min_heap.top());
+        min_heap.pop();
+    }
+
+    return sorted;
+}
+
+}  // namespace sorting
+
+/**
+ * @brief Self-test implementations
+ * @returns void
+ */
+static void tests() {
+    // Test 1: regular unsorted array
+    std::vector<int> arr1 = {5, 3, 1, 4, 2};
+    std::vector<int> sorted1 = sorting::tournament_sort(arr1);
+    assert(std::is_sorted(sorted1.begin(), sorted1.end()));
+
+    // Test 2: already sorted
+    std::vector<int> arr2 = {1, 2, 3, 4, 5};
+    std::vector<int> sorted2 = sorting::tournament_sort(arr2);
+    assert(std::is_sorted(sorted2.begin(), sorted2.end()));
+
+    // Test 3: reverse sorted
+    std::vector<int> arr3 = {5, 4, 3, 2, 1};
+    std::vector<int> sorted3 = sorting::tournament_sort(arr3);
+    assert(std::is_sorted(sorted3.begin(), sorted3.end()));
+
+    // Test 4: single element
+    std::vector<int> arr4 = {42};
+    std::vector<int> sorted4 = sorting::tournament_sort(arr4);
+    assert(std::is_sorted(sorted4.begin(), sorted4.end()));
+
+    // Test 5: empty array
+    std::vector<int> arr5 = {};
+    std::vector<int> sorted5 = sorting::tournament_sort(arr5);
+    assert(sorted5.empty());
+
+    // Test 6: duplicates
+    std::vector<int> arr6 = {3, 1, 2, 1, 3};
+    std::vector<int> sorted6 = sorting::tournament_sort(arr6);
+    assert(std::is_sorted(sorted6.begin(), sorted6.end()));
+
+    // Test 7: negative numbers
+    std::vector<int> arr7 = {-3, 0, -1, 5, 2};
+    std::vector<int> sorted7 = sorting::tournament_sort(arr7);
+    assert(std::is_sorted(sorted7.begin(), sorted7.end()));
+
+    std::cout << "All tests passed!\n";
+}
+
+/**
+ * @brief Main function
+ * @returns 0 on successful exit
+ */
+int main() {
+    tests();
+    return 0;
+}