剑指Offer09 数值的整数次方

 1 /*************************************************************************
 2     > File Name: 09_Power.c
 3     > Author: Juntaran
 4     > Mail: [email protected]
 5     > Created Time: 2016年08月29日 星期一 21时07分21秒
 6  ************************************************************************/
 7
 8 #include <stdio.h>
 9
10 double Power(double base, int exponent)
11 {
12     if (base == 0)
13         return 0;
14     if (exponent == 0)
15         return 1;
16     if (exponent == 1)
17         return base;
18
19     int x = abs(exponent);
20     double r = 1.0;
21
22     while (x)
23     {
24         if (x & 1)
25             r *= base;
26         base *= base;
27         x >>= 1;
28         printf("r is %f\n base is %f\n x is %d\n", r, base, x);
29     }
30     return exponent<0 ? 1/r : r;
31 }
32
33 int main()
34 {
35     double base = 2;
36     int exponent = 10;
37     double ret = Power(base, exponent);
38     printf("ret is %f\n", ret);
39
40     return 0;
41 }