1 /*************************************************************************
2 > File Name: 46_Accumulate.c
3 > Author: Juntaran
4 > Mail: JuntaranMail@gmail.com
5 > Created Time: 2016年09月04日 星期日 21时18分28秒
6 ************************************************************************/
7
8 #include <stdio.h>
9
10 // 函数指针法求1+2+...+n
11 typedef unsigned int (*fun)(unsigned int);
12
13 unsigned int sum_T(int n)
14 {
15 return 0;
16 }
17
18 int Sum1(int n)
19 {
20 static fun f[2] = {sum_T, Sum1};
21 return n + f[!!n](n-1);
22 }
23
24 // 递归
25 int Sum2(int n)
26 {
27 int sum = n;
28 int ans = (n>0) && (sum+=Sum2(n-1));
29 return sum;
30 }
31
32 int main()
33 {
34 int n = 7;
35 int ret1 = Sum1(n);
36 int ret2 = Sum2(n);
37 printf("ret1 is %d\n", ret1);
38 printf("ret2 is %d\n", ret2);
39
40 return 0;
41 }
