Added strand sort algorithm (#1081)

* Create strand_sort.cpp

* Update strand_sort.cpp

* Update strand_sort.cpp

* Delete strand_sort.cpp

* Create strand_sort.cpp

* Update sorting/strand_sort.cpp

Co-authored-by: David Leal <halfpacho@gmail.com>

* Update strand_sort.cpp

* Update strand_sort.cpp

* Update sorting/strand_sort.cpp

Co-authored-by: David Leal <halfpacho@gmail.com>

* Update sorting/strand_sort.cpp

Co-authored-by: David Leal <halfpacho@gmail.com>

* Update strand_sort.cpp

* Update sorting/strand_sort.cpp

Co-authored-by: David Leal <halfpacho@gmail.com>

* Update sorting/strand_sort.cpp

Co-authored-by: David Leal <halfpacho@gmail.com>

* Update sorting/strand_sort.cpp

Co-authored-by: David Leal <halfpacho@gmail.com>

* Update sorting/strand_sort.cpp

Co-authored-by: Krishna Vedala <7001608+kvedala@users.noreply.github.com>

* Update sorting/strand_sort.cpp

Co-authored-by: Krishna Vedala <7001608+kvedala@users.noreply.github.com>

* Update sorting/strand_sort.cpp

Co-authored-by: Krishna Vedala <7001608+kvedala@users.noreply.github.com>

* Update strand_sort.cpp

* Update strand_sort.cpp

* updating DIRECTORY.md

Co-authored-by: David Leal <halfpacho@gmail.com>
Co-authored-by: Krishna Vedala <7001608+kvedala@users.noreply.github.com>
Co-authored-by: github-actions <${GITHUB_ACTOR}@users.noreply.github.com>

DIRECTORY.md

@@ -250,6 +250,7 @@
   * [Shell Sort](https://github.com/TheAlgorithms/C-Plus-Plus/blob/master/sorting/shell_sort.cpp)
   * [Shell Sort2](https://github.com/TheAlgorithms/C-Plus-Plus/blob/master/sorting/shell_sort2.cpp)
   * [Slow Sort](https://github.com/TheAlgorithms/C-Plus-Plus/blob/master/sorting/slow_sort.cpp)
+  * [Strand Sort](https://github.com/TheAlgorithms/C-Plus-Plus/blob/master/sorting/strand_sort.cpp)
   * [Swap Sort](https://github.com/TheAlgorithms/C-Plus-Plus/blob/master/sorting/swap_sort.cpp)
   * [Tim Sort](https://github.com/TheAlgorithms/C-Plus-Plus/blob/master/sorting/tim_sort.cpp)
 

sorting/strand_sort.cpp

@@ -0,0 +1,87 @@
+/**
+ * @file strand_sort.cpp
+ * @brief Implementation of [Strand Sort](https://en.wikipedia.org/wiki/Strand_sort) algorithm.
+ *
+ * @details
+ * Strand Sort is a sorting algorithm that works in \f$O(n)\f$ time if list is already sorted and works in \f$O(n^2)\f$ in worst case.
+ * 
+ * It is passed over the array to be sorted once and the ascending (sequential) numbers are taken.
+ * After the first iteration, the sequential sub-array is put on the empty sorted array.
+ * The main sequence is passed over again and a new sub-sequence is created in order.
+ * Now that the sorted array is not empty, the newly extracted substring is merged with the sorted array.
+ * Repeat types 3 and 4 until the sub-sequence and main sequence are empty.
+ * 
+ * @author [Mertcan Davulcu](https://github.com/mertcandav)
+ */
+#include <iostream>
+#include <list>
+
+/**
+ * @namespace sorting
+ * @brief Sorting algorithms
+ */
+namespace sorting {
+    /**
+    * @namespace strand
+    * @brief Functions for [Strand Sort](https://en.wikipedia.org/wiki/Strand_sort) algorithm
+    */
+    namespace strand {
+        /**
+        * @brief Apply sorting
+        * @tparam element type of list
+        * @param lst List to be sorted
+        * @returns Sorted list<T> instance
+        */
+        template <typename T>
+        std::list<T> strand_sort(std::list<T> lst) {
+            if (lst.size() < 2) { // Returns list if empty or contains only one element
+                return lst; // Returns list
+            }
+            std::list<T> result; // Define new "result" named list instance.
+            std::list<T> sorted; // Define new "sorted" named list instance.
+            while(!lst.empty()) /* if lst is not empty */ {
+                sorted.push_back(lst.front()); // Adds the first element of "lst" list to the bottom of the "sorted" list.
+                lst.pop_front(); // Remove first element of "lst" list.
+                for (auto it = lst.begin(); it != lst.end(); ) { // Return the loop as long as the current iterator is not equal to the last literator of the "lst" list.
+                    if (sorted.back() <= *it) { // If the last reference of the "sorted" list is less than or equal to the current iterator reference.
+                        sorted.push_back(*it); // Adds the iterator retrieved in the loop under the "sorted" list.
+                        it = lst.erase(it); // Deletes the element with the current iterator and assigns the deleted element to the iterator.
+                    } else {
+                        it++; // Next iterator.
+                    }
+                }
+                result.merge(sorted); // Merge "result" list with "sorted" list.
+            }
+            return result; // Returns sorted list
+        }
+    }  // namespace strand
+}  // namespace sorting
+
+/**
+ * @brief Function for testing
+ * @return N/A
+ */
+static void test() {
+    std::list<int> lst = { -333, 525, 1, 0, 94, 52, 33 };
+
+    std::cout << "Before: ";
+    for(auto item: lst) {
+        std::cout << item << " ";
+    }
+
+    lst = sorting::strand::strand_sort(lst); // Sort list.
+
+    std::cout << "\nAfter: ";
+    for(auto item: lst) {
+        std::cout << item << " ";
+    }
+}
+
+/**
+ * @brief Main function
+ * @returns 0 on exit
+ */
+int main() {
+    test();
+    return 0;
+}