Adding Meta Binary Search Algorithm

searching/meta_binary_search.c

@@ -0,0 +1,123 @@
+/**
+ * @file
+ * @brief Program to perform "Meta Binary Search" of a target
+ * value in a given *sorted* array.
+ * @authors [Your Name] - recursive and iterative algorithms
+ */
+
+#include <assert.h>
+#include <stdio.h>
+
+/** Recursive implementation
+ * \param[in] arr array to search
+ * \param[in] l left index of search range
+ * \param[in] r right index of search range
+ * \param[in] x target value to search for
+ * \returns location of x assuming array arr[l..r] is present
+ * \returns -1 otherwise
+ */
+int meta_binary_search_recursive(const int *arr, int l, int r, int x)
+{
+    if (r >= l)
+    {
+        // Calculate the mid-point with a different approach
+        int mid = l + (r - l) / 3;
+
+        // Check if element is present at the calculated mid
+        if (arr[mid] == x)
+            return mid;
+
+        // Calculate second mid-point
+        int mid2 = r - (r - l) / 3;
+
+        // Check if element is present at the second mid
+        if (arr[mid2] == x)
+            return mid2;
+
+        // Recursive search based on value at mid points
+        if (x < arr[mid])
+            return meta_binary_search_recursive(arr, l, mid - 1, x);
+        else if (x > arr[mid2])
+            return meta_binary_search_recursive(arr, mid2 + 1, r, x);
+        else
+            return meta_binary_search_recursive(arr, mid + 1, mid2 - 1, x);
+    }
+
+    // Element is not present in the array
+    return -1;
+}
+
+/** Iterative implementation
+ * \param[in] arr array to search
+ * \param[in] n length of the array
+ * \param[in] x target value to search for
+ * \returns location of x assuming array arr is present
+ * \returns -1 otherwise
+ */
+int meta_binary_search_iterative(const int *arr, int n, int x)
+{
+    int l = 0, r = n - 1;
+
+    while (l <= r)
+    {
+        // Calculate the first mid-point
+        int mid = l + (r - l) / 3;
+
+        // Check if element is present at the first mid
+        if (arr[mid] == x)
+            return mid;
+
+        // Calculate the second mid-point
+        int mid2 = r - (r - l) / 3;
+
+        // Check if element is present at the second mid
+        if (arr[mid2] == x)
+            return mid2;
+
+        // Narrow the search range based on the target value
+        if (x < arr[mid])
+            r = mid - 1;
+        else if (x > arr[mid2])
+            l = mid2 + 1;
+        else
+        {
+            l = mid + 1;
+            r = mid2 - 1;
+        }
+    }
+
+    // Element is not present in the array
+    return -1;
+}
+
+/** Test implementations */
+void test()
+{
+    int arr[] = {2, 3, 4, 10, 40, 50, 60, 70, 80};
+    int n = sizeof(arr) / sizeof(arr[0]);
+
+    printf("Test 1.... ");
+    int x = 10;
+    int result = meta_binary_search_recursive(arr, 0, n - 1, x);
+    assert(result == 3);
+    printf("passed recursive... ");
+    result = meta_binary_search_iterative(arr, n, x);
+    assert(result == 3);
+    printf("passed iterative...\n");
+
+    printf("Test 2.... ");
+    x = 5; // Element not in array
+    result = meta_binary_search_recursive(arr, 0, n - 1, x);
+    assert(result == -1);
+    printf("passed recursive... ");
+    result = meta_binary_search_iterative(arr, n, x);
+    assert(result == -1);
+    printf("passed iterative...\n");
+}
+
+/** Main function */
+int main(void)
+{
+    test();
+    return 0;
+}