feat: add dutch national flag 3 way sort

DIRECTORY.md

@@ -396,6 +396,7 @@
   * [Comb Sort](https://github.com/TheAlgorithms/C/blob/master/sorting/comb_sort.c)
   * [Counting Sort](https://github.com/TheAlgorithms/C/blob/master/sorting/counting_sort.c)
   * [Cycle Sort](https://github.com/TheAlgorithms/C/blob/master/sorting/cycle_sort.c)
+  * [Dnf Sort](https://github.com/TheAlgorithms/C/blob/master/sorting/dnf_sort.c)
   * [Gnome Sort](https://github.com/TheAlgorithms/C/blob/master/sorting/gnome_sort.c)
   * [Heap Sort](https://github.com/TheAlgorithms/C/blob/master/sorting/heap_sort.c)
   * [Heap Sort 2](https://github.com/TheAlgorithms/C/blob/master/sorting/heap_sort_2.c)

sorting/dnf_sort.c

@@ -0,0 +1,129 @@
+/**
+ * @file
+ * @brief Program to perform [dutch national
+ * flag](https://en.wikipedia.org/wiki/Dutch_national_flag_problem) of a target
+ * value in a given {0, 1, 2} containing array.
+ * @details The dutch national flag problem is a computer science programming
+ * problem proposed by Edsger Dijkstra.
+ * Given a length n array of thee values, say red(0), white(1) and blue(2), the
+ * task is to order them by group. This is achieved by moving three pointers and
+ * swapping values depending on the value of the middle pointer.
+ * @author [Bijan Riesenberg](https://github.com/Data-Hero) Iterative
+ */
+#include <assert.h>    /// for assert
+#include <inttypes.h>  /// for the 8 bit sized int8_t type
+#include <stdio.h>     /// for IO operations
+#include <stdlib.h>    /// for memory allocation
+
+/**
+ * @brief Dutch National Flag 3-Way inplace sort algorithm
+ * @param arr array containting elements from {0, 1, 2} to be sorted
+ * @param size size of the array
+ * @returns void
+ */
+void dnfSort(int8_t *arr, int size)
+{
+    int low = 0, mid = 0, high = size - 1;
+    int8_t temp = 0;
+    while (mid <= high)
+    {
+        switch (arr[mid])
+        {
+        case 0:
+            temp = arr[low];
+            arr[low++] = arr[mid];
+            arr[mid++] = temp;
+            break;
+        case 1:
+            ++mid;
+            break;
+        case 2:
+            temp = arr[mid];
+            arr[mid] = arr[high];
+            arr[high--] = temp;
+            break;
+        default:
+            break;
+        }
+    }
+}
+
+/**
+ * @brief Print an array containing int8_t elements
+ * @param arr array containting elements from {0, 1, 2} (int8_t) to be printed
+ * @param size size of the array
+ * @returns void
+ */
+void printArray(int8_t *arr, int size)
+{
+    for (int c = 0; c < size; c++)
+    {
+        c != size - 1 ? printf("%" PRIi8 ", ", arr[c])
+                      : printf("%" PRIi8 "\n", arr[c]);
+    }
+}
+
+/**
+ * @brief Self-test implementations
+ * @returns void
+ */
+static void test()
+{
+    int size = 6;
+    int8_t *arr1 = (int8_t *)malloc(sizeof(int8_t) * size);
+    arr1[0] = 1, arr1[1] = 1, arr1[2] = 1, arr1[3] = 2, arr1[4] = 1,
+    arr1[5] = 0;
+    dnfSort(arr1, size);
+    int8_t compare1[] = {0, 1, 1, 1, 1, 2};
+    for (int c = 0; c < size; c++)
+    {
+        assert(arr1[c] == compare1[c]);
+    }
+    free(arr1);
+
+    size = 1;
+    int8_t *arr2 = (int8_t *)malloc(sizeof(int8_t) * size);
+    arr2[0] = 2;
+    dnfSort(arr2, size);
+    int8_t compare2[] = {2};
+    for (int c = 0; c < size; c++)
+    {
+        assert(arr2[c] == compare2[c]);
+    }
+    free(arr2);
+}
+
+/**
+ * @brief Main Functiuon that reads an array of {0, 1, 2} and use the
+ * Dutch National Flag 3-Way sort algorithm to sort
+ * @returns int 0 if successful 1 if input is not in {0, 1, 2}
+ */
+int main(void)
+{
+    test();  // run self-test implementations
+    int size = 0;
+    printf("Enter size of the array:\n");
+    scanf("%d", &size);  // E.g. 8
+
+    printf("Enter the elements in {0, 1, 2} of the array\n");
+    int i;
+    int8_t *arr = (int8_t *)malloc(sizeof(int8_t) * size);
+    for (i = 0; i < size; i++)
+    {
+        scanf("%" SCNi8, &arr[i]);
+        if (arr[i] > 2 || arr[i] < 0)
+        {
+            printf("Elements need to be in {0, 1, 2}\n");
+            free(arr);
+            return 1;
+        }
+    }
+    printf("Original: \n");
+    printArray(arr, size);
+    dnfSort(arr, size);
+    printf("Sorted: \n");
+    printArray(arr, size);
+
+    free(arr);
+    return 0;
+}