From b98dcdfd08db5441e2683328746844a65bfd6bad Mon Sep 17 00:00:00 2001
From: Ameya Chawla <88154798+ameyachawlaggsipu@users.noreply.github.com>
Date: Sun, 7 Nov 2021 22:06:08 +0530
Subject: [PATCH] feat : Implemented Babylonian Method (#1837)

* feat : Implemented Babylonian Method

Babylonian method is used to calculate  square roots .

* Update numerical_methods/babylonian_method.cpp

Co-authored-by: David Leal <halfpacho@gmail.com>

* updating DIRECTORY.md

* clang-format and clang-tidy fixes for 9596ac79

Co-authored-by: David Leal <halfpacho@gmail.com>
Co-authored-by: github-actions <${GITHUB_ACTOR}@users.noreply.github.com>
---
 DIRECTORY.md                            |   1 +
 numerical_methods/babylonian_method.cpp | 101 ++++++++++++++++++++++++
 2 files changed, 102 insertions(+)
 create mode 100644 numerical_methods/babylonian_method.cpp

diff --git a/DIRECTORY.md b/DIRECTORY.md
index d2c85ebda..964917504 100644
--- a/DIRECTORY.md
+++ b/DIRECTORY.md
@@ -221,6 +221,7 @@
   * [Volume](https://github.com/TheAlgorithms/C-Plus-Plus/blob/master/math/volume.cpp)
 
 ## Numerical Methods
+  * [Babylonian Method](https://github.com/TheAlgorithms/C-Plus-Plus/blob/master/numerical_methods/babylonian_method.cpp)
   * [Bisection Method](https://github.com/TheAlgorithms/C-Plus-Plus/blob/master/numerical_methods/bisection_method.cpp)
   * [Brent Method Extrema](https://github.com/TheAlgorithms/C-Plus-Plus/blob/master/numerical_methods/brent_method_extrema.cpp)
   * [Composite Simpson Rule](https://github.com/TheAlgorithms/C-Plus-Plus/blob/master/numerical_methods/composite_simpson_rule.cpp)
diff --git a/numerical_methods/babylonian_method.cpp b/numerical_methods/babylonian_method.cpp
new file mode 100644
index 000000000..b18bc0dc4
--- /dev/null
+++ b/numerical_methods/babylonian_method.cpp
@@ -0,0 +1,101 @@
+/**
+ * @file
+ * @brief [A babylonian method
+ * (BM)](https://en.wikipedia.org/wiki/Methods_of_computing_square_roots#Babylonian_method)
+ * is an algorithm that computes the square root.
+ * @details
+ * This algorithm has an application in use case scenario where a user wants
+ * find accurate square roots of large numbers
+ * @author [Ameya Chawla](https://github.com/ameyachawlaggsipu)
+ */
+
+#include <cassert>   /// for assert
+#include <iostream>  /// for IO operations
+
+#include "math.h"
+
+/**
+ * @namespace numerical_methods
+ * @brief Numerical algorithms/methods
+ */
+
+namespace numerical_methods {
+
+/**
+ * @brief Babylonian methods is an iterative function which returns
+ * square root of radicand
+ * @param radicand is the radicand
+ * @returns x1 the square root of radicand
+ */
+
+double babylonian_method(double radicand) {
+    int i = 1;  /// To find initial root or rough approximation
+
+    while (i * i <= radicand) {
+        i++;
+    }
+
+    i--;  /// Real Initial value will be i-1 as loop stops on +1 value
+
+    double x0 = i;  /// Storing previous value for comparison
+    double x1 =
+        (radicand / x0 + x0) / 2;  /// Storing calculated value for comparison
+    double temp = NAN;             /// Temp variable to x0 and x1
+
+    while (std::max(x0, x1) - std::min(x0, x1) < 0.0001) {
+        temp = (radicand / x1 + x1) / 2;  /// Newly calculated root
+        x0 = x1;
+        x1 = temp;
+    }
+
+    return x1;  /// Returning final root
+}
+
+}  // namespace numerical_methods
+
+/**
+ * @brief Self-test implementations
+ * @details
+ * Declaring two test cases and checking for the error
+ * in predicted and true value is less than 0.0001.
+ * @returns void
+ */
+static void test() {
+    /* descriptions of the following test */
+
+    auto testcase1 = 125348;  /// Testcase 1
+    auto testcase2 = 752080;  /// Testcase 2
+
+    auto real_output1 = 354.045194855;  /// Real Output 1
+    auto real_output2 = 867.225460881;  /// Real Output 2
+
+    auto test_result1 = numerical_methods::babylonian_method(testcase1);
+    /// Test result for testcase 1
+    auto test_result2 = numerical_methods::babylonian_method(testcase2);
+    /// Test result for testcase 2
+
+    assert(std::max(test_result1, real_output1) -
+               std::min(test_result1, real_output1) <
+           0.0001);
+    /// Testing for test Case 1
+    assert(std::max(test_result2, real_output2) -
+               std::min(test_result2, real_output2) <
+           0.0001);
+    /// Testing for test Case 2
+
+    std::cout << "All tests have successfully passed!\n";
+}
+
+/**
+ * @brief Main function
+ * @param argc commandline argument count (ignored)
+ * @param argv commandline array of arguments (ignored)
+ * calls automated test function to test the working of fast fourier transform.
+ * @returns 0 on exit
+ */
+
+int main(int argc, char const *argv[]) {
+    test();  //  run self-test implementations
+             //  with 2 defined test cases
+    return 0;
+}