資料結構

 1  #include <stdio.h>
 2  #include <string.h>
 3  #define SWAP(A, B) do { char _tmp[sizeof((A))];       \
 4      memcpy(_tmp,&(A),sizeof((A)));                    \
 5      (A)=(B);                                          \
 6      memcpy(&(B),_tmp,sizeof((B)));} while(0)
 7  void perm(char *list, int i, int n) {
 8      int j, temp;
 9      if(i==n){
10          for(j=0;j<=n;j++)
11              printf("%c",list[j]);
12          printf(",");
13      }
14      else {
15          for (j=i;j<=n;j++){
16              SWAP(list[i],list[j]);
17              printf("%d%d,",i,j);  //swap i,j
18              perm(list,i+1,n);
19              printf("%d%d,",j,i);  //swap j,i
20              SWAP(list[j],list[i]);
21          }
22      }
23  }
24  int main(){
25      char str[]="abc";
26      perm(str,0,2);
27      return 0;
28  }