問題：輸入一個字串，打印出該字串中字元的所有排列。例如輸入字串abc，則打印出字元a，b，c所能排列出來的所有字串abc,acb,bac,bca,cab,cba.

思路1:利用STL中的next_permutation(...)來直接實現該功能。要包含標頭檔案#include <algorithm>。

void STLnext_permutation(char *s1, int length)
{
    do
    {
        cout<<s1<<endl;
    }while(next_permutation(s1, s1+length));
    
}
 

void permutation(char *s,char *pBegin)
{
    if(*pBegin == '\0')
    {
        cout<<s<<endl;
    }
    else
    {
        for(char* pCh = pBegin; *pCh != '\0'; ++pCh)
        {
            char temp = *pCh;
            *pCh = *pBegin;
            *pBegin = temp;
            
            permutation(s, pBegin + 1);
            
            temp = *pCh;
            *pCh = *pBegin;
            *pBegin = temp;
            
        }
    }
    
}