feat: add dnf sort (TheAlgorithms#1558)

* add dnf sort * refactored code * remove extra empty lines * add tests * update date type for non-negative values * Update sorting/dnf_sort.cpp Co-authored-by: David Leal <[email protected]> * Update sorting/dnf_sort.cpp Co-authored-by: David Leal <[email protected]> * Update sorting/dnf_sort.cpp Co-authored-by: David Leal <[email protected]> * Update sorting/dnf_sort.cpp Co-authored-by: David Leal <[email protected]> * Update sorting/dnf_sort.cpp Co-authored-by: David Leal <[email protected]> * Update sorting/dnf_sort.cpp Co-authored-by: David Leal <[email protected]> * Update sorting/dnf_sort.cpp Co-authored-by: David Leal <[email protected]> * Update sorting/dnf_sort.cpp Co-authored-by: David Leal <[email protected]> * Update sorting/dnf_sort.cpp Co-authored-by: David Leal <[email protected]> * updating DIRECTORY.md * Update sorting/dnf_sort.cpp Co-authored-by: David Leal <[email protected]> * update data type for variables Co-authored-by: David Leal <[email protected]> Co-authored-by: github-actions <${GITHUB_ACTOR}@users.noreply.github.com>
Rijul24 · Aug 19, 2021 · c3b07ae · c3b07ae
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diff --git a/DIRECTORY.md b/DIRECTORY.md
@@ -298,6 +298,7 @@
  * [Counting Sort](https://github.com/TheAlgorithms/C-Plus-Plus/blob/master/sorting/counting_sort.cpp)
  * [Counting Sort String](https://github.com/TheAlgorithms/C-Plus-Plus/blob/master/sorting/counting_sort_string.cpp)
  * [Cycle Sort](https://github.com/TheAlgorithms/C-Plus-Plus/blob/master/sorting/cycle_sort.cpp)
+ * [Dnf Sort](https://github.com/TheAlgorithms/C-Plus-Plus/blob/master/sorting/dnf_sort.cpp)
  * [Gnome Sort](https://github.com/TheAlgorithms/C-Plus-Plus/blob/master/sorting/gnome_sort.cpp)
  * [Heap Sort](https://github.com/TheAlgorithms/C-Plus-Plus/blob/master/sorting/heap_sort.cpp)
  * [Insertion Sort](https://github.com/TheAlgorithms/C-Plus-Plus/blob/master/sorting/insertion_sort.cpp)

diff --git a/sorting/dnf_sort.cpp b/sorting/dnf_sort.cpp
@@ -0,0 +1,109 @@
+/**
+ * @file
+ * @brief Implementation of the [DNF
+ * sort](https://www.geeksforgeeks.org/sort-an-array-of-0s-1s-and-2s/) implementation
+ * @details
+ * C++ program to sort an array with 0, 1 and 2 in a single pass(DNF sort).
+ * Since one traversal of the array is there hence it works in O(n) time
+ * complexity.
+ * @author [Sujal Gupta](https://github.com/heysujal)
+ */
+
+#include <algorithm> /// for std::is_sorted
+#include <cassert> /// for assert
+#include <iostream> /// for std::swap and io operations
+#include <vector> /// for std::vector
+
+/**
+ * @namespace sorting
+ * @breif Sorting algorithms
+ */
+namespace sorting {
+/**
+ * @namespace dnf_sort
+ * @brief Functions for the [DNF
+ * sort](https://en.wikipedia.org/wiki/Dutch_national_flag_problem) implementation
+ */
+namespace dnf_sort {
+/**
+ * @brief The main function implements DNF sort
+ * @tparam T type of array
+ * @param a array to be sorted,
+ * @param arr_size size of array
+ * @returns void
+ */
+template <typename T>
+std::vector<T> dnfSort(const std::vector<T> &in_arr) {
+ std::vector<T> arr(in_arr);
+ uint64_t lo = 0;
+ uint64_t hi = arr.size() - 1;
+ uint64_t mid = 0;
+
+ // Iterate till all the elements
+ // are sorted
+ while (mid <= hi) {
+ switch (arr[mid]) {
+ // If the element is 0
+ case 0:
+ std::swap(arr[lo++], arr[mid++]);
+ break;
+
+ // If the element is 1 .
+ case 1:
+ mid++;
+ break;
+
+ // If the element is 2
+ case 2:
+ std::swap(arr[mid], arr[hi--]);
+ break;
+ }
+ }
+ return arr;
+}
+} // namespace dnf_sort
+} // namespace sorting
+
+/**
+ * @brief Self-test implementations
+ * @returns void
+ */
+static void test() {
+ // 1st test
+ // [1, 0, 2, 1] return [0, 1, 1, 2]
+ std::vector<uint64_t> array1 = {0, 1, 1, 2};
+ std::cout << "Test 1... ";
+ std::vector<uint64_t> arr1 = sorting::dnf_sort::dnfSort(array1);
+ assert(std::is_sorted(std::begin(arr1), std::end(arr1)));
+ std::cout << "passed" << std::endl;
+ // 2nd test
+ // [1, 0, 0, 1, 1, 0, 2, 1] return [0, 0, 0, 1, 1, 1, 1, 2]
+ std::vector<uint64_t> array2 = {1, 0, 0, 1, 1, 0, 2, 1};
+ std::cout << "Test 2... ";
+ std::vector<uint64_t> arr2 = sorting::dnf_sort::dnfSort(array2);
+ assert(std::is_sorted(std::begin(arr2), std::end(arr2)));
+ std::cout << "passed" << std::endl;
+ // 3rd test
+ // [1, 1, 0, 0, 1, 2, 2, 0, 2, 1] return [0, 0, 0, 1, 1, 1, 1, 2, 2, 2]
+ std::vector<uint64_t> array3 = {1, 1, 0, 0, 1, 2, 2, 0, 2, 1};
+ std::cout << "Test 3... ";
+ std::vector<uint64_t> arr3 = sorting::dnf_sort::dnfSort(array3);
+ assert(std::is_sorted(std::begin(arr3), std::end(arr3)));
+ std::cout << "passed" << std::endl;
+ // 4th test
+ // [2, 2, 2, 0, 0, 1, 1] return [0, 0, 1, 1, 2, 2, 2]
+ std::vector<uint64_t> array4 = {2, 2, 2, 0, 0, 1, 1};
+ std::cout << "Test 4... ";
+ std::vector<uint64_t> arr4 = sorting::dnf_sort::dnfSort(array4);
+ assert(std::is_sorted(std::begin(arr4), std::end(arr4)));
+ std::cout << "passed" << std::endl;
+}
+
+/**
+ * @brief Main function
+ * @returns 0 on exit
+ */
+int main() {
+ test(); // execute the test
+ return 0;
+}