数据结构练习（21）字符串的排列

http://zhedahht.blog.163.com/blog/static/254111742007499363479/

很经典的题目，考察对递归的理解。

#include <cstdio>
#include <cstring>

void swap(char* ch1, char* ch2)
{
    if (ch1 && ch2)
    {
        char ch = *ch1;
        *ch1 = *ch2;
        *ch2 = ch;
    }
}

void permutation(char* str, char* begin)
{
    if (str && begin)
    {
        if (*begin == '\0')
            printf("%s\n", str);
        else 
        {
            for (char *p = begin; *p != '\0'; ++p)
            {
                swap(begin, p);
                permutation(str, begin + 1);
                swap(begin, p);
            }
        }
    }
}

void permutation(char *str)
{
    if (str)
        permutation(str, str);
}

int main()
{
    char b[100];

    while (scanf("%s", b) != EOF)
        permutation(b);

    return 0;
}