Added math function power (#604)

* added power algorithm

* updating DIRECTORY.md

* make test function static

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

* Update misc/power_recursion.c

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

* Update misc/power_recursion.c

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

* Update misc/power.c

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

* Update misc/power.c

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

* Update misc/power.c

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

* Update misc/power.c

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

* Update misc/power_recursion.c

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

* Update misc/power_recursion.c

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

* Update misc/power.c

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

* Update misc/power_recursion.c

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

* Update misc/power_recursion.c

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

* Update misc/power.c

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

* Update misc/power.c

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

* Update misc/power_recursion.c

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

* Update misc/power.c

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

DIRECTORY.md

@@ -249,6 +249,8 @@
   * [Palindrome](https://github.com/TheAlgorithms/C/blob/master/misc/palindrome.c)
   * [Pid](https://github.com/TheAlgorithms/C/blob/master/misc/pid.c)
   * [Poly Add](https://github.com/TheAlgorithms/C/blob/master/misc/poly_add.c)
+  * [Power](https://github.com/TheAlgorithms/C/blob/master/misc/power.c)
+  * [Power Recursion](https://github.com/TheAlgorithms/C/blob/master/misc/power_recursion.c)
   * [Prime](https://github.com/TheAlgorithms/C/blob/master/misc/prime.c)
   * [Prime Factoriziation](https://github.com/TheAlgorithms/C/blob/master/misc/prime_factoriziation.c)
   * [Quartile](https://github.com/TheAlgorithms/C/blob/master/misc/quartile.c)

misc/power.c

@@ -0,0 +1,47 @@
+/**
+ * @file
+ * @brief Program to calculate
+ * [exponentiation](https://en.wikipedia.org/wiki/Exponentiation)
+ *
+ * @author [Du Yuanchao](https://github.com/shellhub)
+ */
+#include <assert.h>
+
+/**
+ * @brief Returns the value of the first argument raised to the power of the
+ * second argument.
+ * @param a the base.
+ * @param b the exponent.
+ * @returns the value {@code a}<sup>{@code b}</sup>.
+ */
+long power(int a, int b)
+{
+    long result = 1;
+    for (int i = 1; i <= b; ++i)
+    {
+        result *= a;
+    }
+    return result;
+}
+
+/**
+ * @brief Test function
+ * @return void
+ */
+static void test()
+{
+    assert(power(0, 2) == 0);
+    assert(power(2, 3) == 8);
+    assert(power(2, 10) == 1024);
+    assert(power(3, 3) == 27);
+}
+
+/**
+ * @brief Driver Code
+ * @returns 0 on exit
+ */
+int main()
+{
+    test();
+    return 0;
+}

misc/power_recursion.c

@@ -0,0 +1,40 @@
+/**
+ * @file
+ * @brief Program to calculate
+ * [exponentiation](https://en.wikipedia.org/wiki/Exponentiation) using
+ * recursion algorithm.
+ *
+ * @author [Du Yuanchao](https://github.com/shellhub)
+ */
+#include <assert.h>
+
+/**
+ * @brief Returns the value of the first argument raised to the power of the
+ * second argument using recursion.
+ * @param a the base.
+ * @param b the exponent.
+ * @returns the value {@code a}<sup>{@code b}</sup>.
+ */
+long power(int a, int b) { return b == 0 ? 1 : a * power(a, b - 1); }
+
+/**
+ * @brief Test function
+ * @return void
+ */
+static void test()
+{
+    assert(power(0, 2) == 0);
+    assert(power(2, 3) == 8);
+    assert(power(2, 10) == 1024);
+    assert(power(3, 3) == 27);
+}
+
+/**
+ * @brief Driver Code
+ * @returns 0 on exit
+ */
+int main()
+{
+    test();
+    return 0;
+}