added selection_sort_recursive.c

sorting/selection_sort_recursive.c

@@ -0,0 +1,100 @@
+/**
+ * @file
+ * @brief [Selection Sort](https://en.wikipedia.org/wiki/Selection_sort)
+ * implementation using recursion.
+ */
+#include <assert.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <time.h>
+
+/**
+ * Swapped two numbers using pointer
+ * @param first first pointer of first number
+ * @param second second pointer of second number
+ */
+void swap(int *first, int *second)
+{
+    int temp = *first;
+    *first = *second;
+    *second = temp;
+}
+
+/**
+ * returned the index having minimum value using recursion
+ *  @param arr array to be sorted
+ * @param size size of array
+*/
+int findIndex(int *arr, int size)
+{
+    if (size == 1)
+    {
+        return 0;
+    }
+
+    // marking recursive call to reach starting element
+    int min_index = findIndex(arr, size - 1);
+
+    if (arr[size - 1] < arr[min_index])
+    {
+        min_index = size - 1;
+    }
+
+    return min_index;
+}
+
+/**
+ * Selection Sort algorithm implemented using recursion
+ * @param arr array to be sorted
+ * @param size size of array
+ */
+void selectionSort(int *arr, int size)
+{
+    if (size == 1)
+    {
+        return;
+    }
+
+    /* findIndex(arr, size) returned the index having min value*/
+    int min_index = findIndex(arr, size);
+    /* arr[min_index] is the minimum value in the array*/
+
+    if (min_index != 0)
+    {
+        swap(&arr[0], &arr[min_index]);
+    }
+
+    /*sorted the remaining array recursively*/
+    selectionSort(arr + 1, size - 1);
+}
+
+/**
+ * Test function
+ */
+void test()
+{
+    const int size = 10;
+    int *arr = (int *)calloc(size, sizeof(int));
+
+    /* generate size random numbers from 0 to 100 */
+    for (int i = 0; i < size; i++)
+    {
+        arr[i] = rand() % 100;
+    }
+    selectionSort(arr, size);
+    for (int i = 0; i < size - 1; ++i)
+    {
+        assert(arr[i] <= arr[i + 1]);
+    }
+    free(arr);
+}
+
+/** Driver Code */
+int main()
+{
+    /* Intializes random number generator */
+    srand(time(NULL));
+    test();
+    return 0;
+}