Add C++ implementation

Signed-off-by: begeekmyfriend <begeekmyfriend@gmail.com>

Author: begeekmyfriend

0050_pow/pow.c

@@ -2,15 +2,16 @@
 #include <stdio.h>
 #include <stdlib.h>
 
-static double fast_pow(double x, int n)
+
+double fast_pow(double x, int n)
 {
     if (n == 0) { return 1.0; }
     if (n == 1) { return x; }
     double t = fast_pow(x, n / 2);
     return n & 1 ? t * t * x : t * t;
 }
 
-static double my_pow(double x, int n)
+double my_pow(double x, int n)
 {
     if (n == INT_MIN) {
         double t = 1 / fast_pow(x, -(n / 2));