字符全排列

#include<stdio.h>#include<string.h>void exchange(char *p,char *q){        if(*p!=*q)        {                *p=*p^*q;                *q=*p^*q;                *p=*p^*q;        }}void permutation(char *pstr,char *pbegin){        char *current;        if(*pbegin=='\0')        {                printf("%s\n",pstr);        }        else        {                for(current=pbegin;*current!='\0';current++)                {                        exchange(pbegin,current);                        permutation(pstr,pbegin+1);                        exchange(pbegin,current);                }        }}void fullname(char *ptr){        if(ptr==NULL)        {                return ;        }        permutation(ptr,ptr);}int main(int argc,char *argv[]){        char ptr[]="key";        fullname(ptr);}