From 9154d5a25dde12744898c5d5cd19ab9c1b3f0268 Mon Sep 17 00:00:00 2001
From: Krishna Vedala <krishna.vedala@ieee.org>
Date: Wed, 27 May 2020 16:22:22 -0400
Subject: [PATCH] docs for large number power

---
 math/power_for_huge_numbers.cpp | 147 ++++++++++++++++----------------
 1 file changed, 73 insertions(+), 74 deletions(-)

diff --git a/math/power_for_huge_numbers.cpp b/math/power_for_huge_numbers.cpp
index bf9374228..5cb1ae514 100644
--- a/math/power_for_huge_numbers.cpp
+++ b/math/power_for_huge_numbers.cpp
@@ -1,91 +1,90 @@
+/**
+ * @file
+ * @brief Compute powers of large numbers
+ */
 #include <iostream>
-using namespace std;
 
-// Maximum number of digits in output
-// x^n where 1 <= x, n <= 10000 and overflow may happen
+/** Maximum number of digits in output
+ *  \f$x^n\f$ where \f$1 <= x,\; n <= 10000\f$ and overflow may happen
+ */
 #define MAX 100000
 
-// This function multiplies x
-// with the number represented by res[].
-// res_size is size of res[] or
-// number of digits in the number
-// represented by res[]. This function
-// uses simple school mathematics
-// for multiplication.
-// This function may value of res_size
-// and returns the new value of res_size
-int multiply(int x, int res[], int res_size)
-{
+/** This function multiplies x
+ * with the number represented by res[].
+ * res_size is size of res[] or
+ * number of digits in the number
+ * represented by res[]. This function
+ * uses simple school mathematics
+ * for multiplication.
+ * This function may value of res_size
+ * and returns the new value of res_size
+ * @param x multiplicand
+ * @param res large number representation using array
+ * @param res_size number of digits in `res`
+ */
+int multiply(int x, int res[], int res_size) {
+    // Initialize carry
+    int carry = 0;
 
-	// Initialize carry
-	int carry = 0;
+    // One by one multiply n with
+    // individual digits of res[]
+    for (int i = 0; i < res_size; i++) {
+        int prod = res[i] * x + carry;
 
-	// One by one multiply n with
-	// individual digits of res[]
-	for (int i = 0; i < res_size; i++)
-	{
-		int prod = res[i] * x + carry;
+        // Store last digit of
+        // 'prod' in res[]
+        res[i] = prod % 10;
 
-		// Store last digit of
-		// 'prod' in res[]
-		res[i] = prod % 10;
+        // Put rest in carry
+        carry = prod / 10;
+    }
 
-		// Put rest in carry
-		carry = prod / 10;
-	}
-
-	// Put carry in res and
-	// increase result size
-	while (carry)
-	{
-		res[res_size] = carry % 10;
-		carry = carry / 10;
-		res_size++;
-	}
-	return res_size;
+    // Put carry in res and
+    // increase result size
+    while (carry) {
+        res[res_size] = carry % 10;
+        carry = carry / 10;
+        res_size++;
+    }
+    return res_size;
 }
 
-// This function finds
-// power of a number x
-void power(int x, int n)
-{
+/** This function finds power of a number x and print \f$x^n\f$
+ * @param x base
+ * @param n exponent
+ */
+void power(int x, int n) {
+    // printing value "1" for power = 0
+    if (n == 0) {
+        std::cout << "1";
+        return;
+    }
 
-	//printing value "1" for power = 0
-	if (n == 0)
-	{
-		cout << "1";
-		return;
-	}
+    int res[MAX];
+    int res_size = 0;
+    int temp = x;
 
-	int res[MAX];
-	int res_size = 0;
-	int temp = x;
+    // Initialize result
+    while (temp != 0) {
+        res[res_size++] = temp % 10;
+        temp = temp / 10;
+    }
 
-	// Initialize result
-	while (temp != 0)
-	{
-		res[res_size++] = temp % 10;
-		temp = temp / 10;
-	}
+    // Multiply x n times
+    // (x^n = x*x*x....n times)
+    for (int i = 2; i <= n; i++) res_size = multiply(x, res, res_size);
 
-	// Multiply x n times
-	// (x^n = x*x*x....n times)
-	for (int i = 2; i <= n; i++)
-		res_size = multiply(x, res, res_size);
-
-	cout << x << "^" << n << " = ";
-	for (int i = res_size - 1; i >= 0; i--)
-		cout << res[i];
+    std::cout << x << "^" << n << " = ";
+    for (int i = res_size - 1; i >= 0; i--) std::cout << res[i];
 }
 
-// Driver program
-int main()
-{
-	int exponent, base;
-	printf("Enter base ");
-	scanf("%id \n", &base);
-	printf("Enter exponent ");
-	scanf("%id", &exponent);
-	power(base, exponent);
-	return 0;
+/** Main function */
+int main() {
+    int exponent, base;
+    printf("Enter base ");
+    scanf("%id \n", &base);
+    printf("Enter exponent ");
+    scanf("%id", &exponent);
+    power(base, exponent);
+    return 0;
 }