1 #include<stdio.h>
 2 void sort(int *pa,int *pb){//a,b按照从大到小的次序排列(利用了指针，实现“双向”传递)
 3     int t;
 4     if(*pa<*pb){
 5         t=*pa;*pa=*pb;*pb=t;
 6     }
 7 }
 8 int gcd_1(int a,int b){//用辗转相除法求最大公约数
 9     int c;
10     if(b!=0){
11         while(a%b!=0){
12             c=b;
13             b=a%b;
14             a=c;
15         }
16     }
17     return b;
18 }
19 int gcd_2(int a,int b){//辗转相除法的递归写法
20     int c;
21     if(b==0)c=a;
22     else
23         c=gcd_2(b,a%b);
24     return c;
25 }
26 int main(){
27     int x,y,z,z2,*pa,*pb;
28     scanf("%d%d",&x,&y);
29     pa=&x,pb=&y;         //若此处改为*pa=x,*pb=y；则pa、pb为野指针
30     sort(pa,pb);
31     z=gcd_1(x,y);
32     z2=gcd_2(x,y);
33     printf("%d\n%d\n",z,z2);
34     return 0;
35 }