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;

}