版权声明：本文为博主原创文章，未经博主允许不得转载。 https://blog.csdn.net/qq_21149391/article/details/79572760
#include<stdio.h>
int main(){
void prin(char s[],int n,int sign,char *p);
char s[3] = {'A','B','C'};
int n;
scanf("%d",&n);
char p[3] = {'\0'};
prin(s,n,0,p);
printf("\n");
}
void prin(char s[],int n,int sign,char p[]){//p存放此位之前的字符
int i,j;
if(n==sign){
printf(",");
return;
}
for(i=0;i<3;i++){
if(sign>0&&i>0){
for(j=0;j<sign;j++)
printf("%c",p[j]);
}
printf("%c",s[i]);
if(sign<n-1)
p[sign] = s[i];
prin(s,n,sign+1,p);
}
}