chore: import upstream snapshot with attribution

math/power_for_huge_numbers.cpp

@@ -0,0 +1,90 @@
+/**
+ * @file
+ * @brief Compute powers of large numbers
+ */
+#include <iostream>
+
+/** 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
+ * @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;
+
+    // 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;
+
+        // 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;
+}
+
+/** 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;
+    }
+
+    int res[MAX];
+    int res_size = 0;
+    int temp = x;
+
+    // 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);
+
+    std::cout << x << "^" << n << " = ";
+    for (int i = res_size - 1; i >= 0; i--) std::cout << res[i];
+}
+
+/** Main function */
+int main() {
+    int exponent, base;
+    std::cout << "Enter base ";
+    std::cin >> base;
+    std::cout << "Enter exponent ";
+    std::cin >> exponent;
+    power(base, exponent);
+    return 0;
+}