n个元素的全排列算法

/* 
* 输出n个元素的全排列 
*/ 

#include <stdio.h> 

void arrange(char *s, int k, int m); 
void swap(char *s1, char *s2); 

int main(void) 
{ 
int n; 
int i; 
char *set; 

printf("Please input the number of elements (>=0): "); 
scanf("%d", &n); 
if (n <= 0) { 
printf("WARN! The number should be >= 1!\n"); 
exit(0); 
} 

set = (char *)calloc(n, sizeof(char)); /* 分配存放集合元素的空间 */ 
if (!set) { 
printf("Sorry! Not enough memory!\n"); 
exit(0); 
} 



/* 读取字符元素 , 限制了输入格式 */ 
printf("Please input the elements ('X X X ...'):\n\t"); 
for (i = 0; i < n; i++) 
/* Notice the '%ls' : get the next non-blank character */ 
scanf("%ls", &set[i]); 

printf("The set is: {"); 
for (i = 0; i < n - 1; i++) 
printf("%c, ", set[i]); 
printf("%c}\n", set[i]); 

printf("All arragnement is as follows:\n"); 
arrange(set, 0, n-1); 

free(set); 

getchar(); /* 防止输出窗口一闪关闭 */ 
getchar(); 

return 0; 
} 

void arrange(char *s, int k, int m) 
{ 
int i; 

if (k == m) { 
printf("\t"); 
for (i = 0; i <= m; i++) 
printf("%c", s[i]); 
printf("\n"); 
} else { 
for (i = k; i <= m; i++) { 
swap(&s[k], &s[i]); 
arrange(s, k + 1, m); 
swap(&s[k], &s[i]); 
} 
} 
} 

void swap(char *s1, char *s2) 
{ 
char temp = *s1; 
*s1 = *s2; 
*s2 = temp; 
}