三个字母的全排列

以A，B,C为例

# include<iostream>
using namespace std;
int main()
{
    char  c1,c2,c3;
    for (c1='A'; c1<='C'; ++c1)
        for (c2='A'; c2<='C'; ++c2)
            if (c1 ==c2) continue;
            else  for (c3='A'; c3<='C'; ++c3)
                    if  ((c3==c1||c3==c2))
                        continue;
                    else cout << c1 <<c2<<c3<<endl;
}