From 969e916871f3e168506c8968008fded8122e7a74 Mon Sep 17 00:00:00 2001
From: Krishna Vedala <krishna.vedala@ieee.org>
Date: Thu, 28 May 2020 19:54:37 -0400
Subject: [PATCH] document exponential search

---
 search/exponential_search.cpp | 62 +++++++++++++++++++++++------------
 1 file changed, 41 insertions(+), 21 deletions(-)

diff --git a/search/exponential_search.cpp b/search/exponential_search.cpp
index 79f09e38b..f57cbf96b 100644
--- a/search/exponential_search.cpp
+++ b/search/exponential_search.cpp
@@ -1,20 +1,42 @@
-// Copyright 2020 Divide-et-impera-11
+/**
+ * \file
+ * \brief [Exponential search
+ * algorithm](https://en.wikipedia.org/wiki/Exponential_search)
+ * \copyright 2020 Divide-et-impera-11
+ *
+ * The algorithm try to search the range where the key should be.
+ * If it has been found we do a binary search there.
+ * The range of the search grows by exponential every time.
+ * If the key is larger than the last element of array, the start of
+ * block(block_front) will be equal to the end of block(block_size) and the
+ * algorithm return null ponter, every other cases the algoritm return fom the
+ * loop.
+ */
 #include <cassert>
 #include <cmath>
 #include <iostream>
-#include <string>
+#ifdef _MSC_VER
+#include <string>  // use for MS Visual C++
+#else
+#include <cstring>  // for all other compilers
+#endif
 
-// Binary Search Algorithm(use by struzik algorithm)
-// Time Complexity O(log n) where 'n' is the number of elements
-// Worst Time Complexity O(log n)
-// Best Time Complexity Ω(1)
-// Space Complexity O(1)
-// Auxiliary Space Complexity O(1)
+/** Binary Search Algorithm (used by ::struzik_search)\n
+ * * Time Complexity O(log n) where 'n' is the number of elements
+ * * Worst Time Complexity O(log n)
+ * * Best Time Complexity Ω(1)
+ * * Space Complexity O(1)
+ * * Auxiliary Space Complexity O(1)
+ * \returns pointer to value in the array
+ * \returns `nullptr` if value not found
+ */
 template <class Type>
 inline Type* binary_s(Type* array, size_t size, Type key) {
     int32_t lower_index(0), upper_index(size - 1), middle_index;
+
     while (lower_index <= upper_index) {
         middle_index = std::floor((lower_index + upper_index) / 2);
+
         if (*(array + middle_index) < key)
             lower_index = (middle_index + 1);
         else if (*(array + middle_index) > key)
@@ -22,21 +44,17 @@ inline Type* binary_s(Type* array, size_t size, Type key) {
         else
             return (array + middle_index);
     }
+
     return nullptr;
 }
-// Struzik Search Algorithm(Exponential)
-// Time Complexity O(log i)where i is the position of search key in the list
-// Worst Time Complexity O(log i)
-// Best Time Complexity Ω(1)
-// Space Complexity O(1)
-// Auxiliary Space Complexity O(1)
-/* Tha algorithm try to search the range where the key should be.
-If it has been found we do a binary search there.
-The range of the search grows by exponential every time.
-If the key is larger than the last element of array,
-the start of block(block_front) will be equal to the end of block(block_size)
-and the algorithm return null ponter,
-every other cases the algoritm return fom the loop. */
+
+/** Struzik Search Algorithm(Exponential)
+ * * Time Complexity O(log i) where i is the position of search key in the list
+ * * Worst Time Complexity O(log i)
+ * * Best Time Complexity Ω(1)
+ * * Space Complexity O(1)
+ * * Auxiliary Space Complexity O(1)
+ */
 template <class Type>
 Type* struzik_search(Type* array, size_t size, Type key) {
     uint32_t block_front(0), block_size = size == 0 ? 0 : 1;
@@ -51,6 +69,8 @@ Type* struzik_search(Type* array, size_t size, Type key) {
     }
     return nullptr;
 }
+
+/** Main function */
 int main() {
     // TEST CASES
     int* sorted_array = new int[7]{7, 10, 15, 23, 70, 105, 203};