以下程序的输出结果是 #include"stdio.h" sub1(char a,char b) {char c; c=a;a=b;b=c;} sub2(char* a,char b) {char c; c=*a;*a=b;b=c;} sub3(char* a,char*b) {char c; c=*a;*a=*b;*b=c;} main() { char a,b; a= ' A ' ;b= ' B ' ;sub3(&a,&b);putchar(a);putchar(b); a= ' A ' ;b= ' B ' ;sub2(&a,b);putchar(a);putchar(b); a= ' A ' ;b= ' B ' ;sub1(a,b);putchar(a);putchar(b); }