#include<iostream.h>
void main()
{
    char a[8],b[8];

    int i=0,j=0;
    cout<<"please input a:";
    do
    {
        cin>>a[i];
    }while(a[i]!='\n');
    cout<<"please input b:";
    do
    {
        cin>>b[i];
    }while(b[i]!='\n');
        
    if(a[0]==b[0])
        cout<<"they are equal!"<<endl;
    else if(a[0]=='r'&&b[0]=='s')
        cout<<"the winner is a!"<<endl;
    else if(a[0]=='r'&&b[0]=='c')
        cout<<"the winner is b!"<<endl;
    else if(a[0]=='c'&&b[0]=='s')
        cout<<"the winner is b!"<<endl;
    else if(a[0]=='c'&&b[0]=='r')
        cout<<"the winner is a!"<<endl;
    else if(a[0]=='s'&&b[0]=='r')
        cout<<"the winner is b!"<<endl;
    else if(a[0]=='s'&&b[0]=='c')
        cout<<"the winner is a!"<<endl;
}
红色字输出不了，前面的赋值也不成功，求解释

變量i一直是0

同2楼，do-while循环，请问第一个循环怎么结束。最后的运行的结果就是一遍又一遍的给a[0]赋值。do-while死循环，语句不会结束，当然不会进行后面的

#include<iostream.h>
void main()
{
    char a[8],b[8];
    int i=0,j=0;



    cout<<"please input a:";
    cin>>a[i];
    while(a[i]!='\n')
    {
        i++;
        cin>>a[i];
    }
    cout<<"please input b:";
    cin>>b[j];
    while(b[j]!='\n')
    {
        j++;
        cin>>b[j];
    }


        
    if(a[0]==b[0])
        cout<<"they are equal!"<<endl;
    else if(a[0]=='r'&&b[0]=='s')
        cout<<"the winner is a!"<<endl;
    else if(a[0]=='r'&&b[0]=='c')
        cout<<"the winner is b!"<<endl;
    else if(a[0]=='c'&&b[0]=='s')
        cout<<"the winner is b!"<<endl;
    else if(a[0]=='c'&&b[0]=='r')
        cout<<"the winner is a!"<<endl;
    else if(a[0]=='s'&&b[0]=='r')
        cout<<"the winner is b!"<<endl;
    else if(a[0]=='s'&&b[0]=='c')
        cout<<"the winner is a!"<<endl;
}
很不好意思，我改了一下，还是不行，能不能帮忙再看看，谢谢了。。

'\n'不是字符所以它进不来了数组，所以你循环是死循环。将'\n'改成别的字符就好了！请看下面程序：
#include<iostream.h>
 void main()
 {
     char a[8],b[8];
     int i=0,j=0;
 


    cout<<"please input a:";
     cin>>a[i];
     while(a[i]!='n')
     {
         i++;
         cin>>a[i];
     }
     cout<<"please input b:";
     cin>>b[j];
     while(b[j]!='n')
     {
         j++;
         cin>>b[j];
     }   
     if(a[0]==b[0])
         cout<<"they are equal!"<<endl;
     else if(a[0]=='r'&&b[0]=='s')
         cout<<"the winner is a!"<<endl;
     else if(a[0]=='r'&&b[0]=='c')
         cout<<"the winner is b!"<<endl;
     else if(a[0]=='c'&&b[0]=='s')
         cout<<"the winner is b!"<<endl;
     else if(a[0]=='c'&&b[0]=='r')
         cout<<"the winner is a!"<<endl;
     else if(a[0]=='s'&&b[0]=='r')
         cout<<"the winner is b!"<<endl;
     else if(a[0]=='s'&&b[0]=='c')
         cout<<"the winner is a!"<<endl;
 }

#include <iostream>
using namespace std;

int main()
{
    char a[8],b[8];

    ios::fmtflags save = cin.flags() & ios::skipws;
    cin.unsetf( ios::skipws );

    cout << "please input a:";
    for( int i=0; ; ++i )
    {
        if( i==7 )
        {
            a[i] = '\0';
            break;
        }

        cin >> noskipws >> a[i];
        if( a[i] == '\n' )
        {
            a[i] = '\0';
            break;
        }
    }

    cout << "please input b:";
    for( int i=0; ; ++i )
    {
        if( i==7 )
        {
            b[i] = '\0';
            break;
        }

        cin >> b[i];
        if( b[i] == '\n' )
        {
            b[i] = '\0';
            break;
        }
    }

    cin.setf( save );

    …………

    return 0;
}

不过，与其这么麻烦，为什么不用 string line; getlin(cin,line) ？？？

LZ应该是新手，他这个程序是培养逻辑思维能力，你说的这个可以当做LZ的提高训练。

新手一般对标准库不太了解，何谈使用乎？
string line; getlin(cin,line); 这些都是标准库里面的东西，LZ是不是能看懂还不知道。