feat: Add the floyd_cycle_detection_algo.cpp file/algorithm (TheAlgor…

…ithms#1540)

* search for duplicate number using Floyd algorithm

* Update floyd_cycle_detection_algo.cpp

Co-authored-by: David Leal <[email protected]>

search/floyd_cycle_detection_algo.cpp

@@ -0,0 +1,96 @@
+/**
+ * @file
+ * @brief Implementation of [Floyd's Cycle
+ * Detection](https://en.wikipedia.org/wiki/Cycle_detection) algorithm
+ * @details
+ * Given an array of integers containing 'n + 1' integers, where each
+ * integer is in the range [1, n] inclusive. If there is only one duplicate
+ * number in the input array, this algorithm returns the duplicate number in
+ * O(1) space and the time complexity is less than O(n^2) without modifying the
+ * original array, otherwise, it returns -1.
+ * @author [Swastika Gupta](https://github.com/Swastyy)
+ */
+
+#include <cassert>   /// for assert
+#include <iostream>  /// for IO operations
+#include <vector>    /// for std::vector
+
+/**
+ * @namespace search
+ * @brief Search algorithms
+ */
+namespace search {
+/**
+ * @namespace cycle_detection
+ * @brief Functions for the [Floyd's Cycle
+ * Detection](https://en.wikipedia.org/wiki/Cycle_detection) algorithm
+ */
+namespace cycle_detection {
+/**
+ * @brief The main function implements search algorithm
+ * @tparam T type of array
+ * @param in_arr the input array
+ * @param n size of array
+ * @returns the duplicate number
+ */
+template <typename T>
+int32_t duplicateNumber(const std::vector<T> &in_arr, const uint32_t &n) {
+    if (n == 0 || n == 1) {  // to find duplicate in an array its size should be atleast 2
+        return -1;
+    }
+    uint32_t tortoise = in_arr[0];  // variable tortoise is used for the longer
+                                    // jumps in the array
+    uint32_t hare = in_arr[0];  // variable hare is used for shorter jumps in the array
+    do {
+        tortoise = in_arr[tortoise];
+        hare = in_arr[in_arr[hare]];
+    } while (tortoise != hare);
+    tortoise = in_arr[0];
+    while (tortoise != hare) {
+        tortoise = in_arr[tortoise];
+        hare = in_arr[hare];
+    }
+    return tortoise;
+}
+}  // namespace cycle_detection
+}  // namespace search
+
+/**
+ * @brief Self-test implementations
+ * @returns void
+ */
+static void test() {
+    // 1st test
+    // [3, 4, 8, 5, 9, 1, 2, 6, 7, 4] return 4
+    std::vector<uint32_t> array1 = {3, 4, 8, 5, 9, 1, 2, 6, 7, 4};
+    std::cout << "Test 1... ";
+    assert(search::cycle_detection::duplicateNumber(array1, array1.size()) ==
+           4);  // here the duplicate number is 4
+    std::cout << "passed" << std::endl;
+
+    // 2nd test
+    // [1, 2, 3, 4, 2] return 2
+    std::vector<uint32_t> array2 = {1, 2, 3, 4, 2};
+    std::cout << "Test 2... ";
+    assert(search::cycle_detection::duplicateNumber(array2, array2.size()) ==
+           2);  // here the duplicate number is 2
+    std::cout << "passed" << std::endl;
+
+    // 3rd test
+    // [] return -1
+    std::vector<uint32_t> array3 = {};
+    std::cout << "Test 3... ";
+    assert(search::cycle_detection::duplicateNumber(array3, array3.size()) ==
+           -1);  // since the input array is empty no duplicate number exists in
+                 // this case
+    std::cout << "passed" << std::endl;
+}
+
+/**
+ * @brief Main function
+ * @returns 0 on exit
+ */
+int main() {
+    test();  // run self-test implementations
+    return 0;
+}