RC4编程为何加密结果是乱码，而且求逆解码的结果与明文不同，多谢~

Question

#include
#include
using namespace std;

void main()
{
char k[256];
int s[256],t[256];

cout<<"please input key"<<endl;
cin>>k;
cout<<endl;

for(int i=0;i<256;i++)
{
    s[i]=i;
    t[i]=k[i%strlen(k)];                            //将输入的密钥扩展为256位
}

int j=0;
for(i=0;i<256;i++)
{
    int temp;
    j=(j+s[i]+t[i])%256;

    temp=s[i];
    s[i]=s[j];
    s[j]=temp;                                              //s-box的变换，打乱原有的顺序

}

cout<<"please input plaintext"<<endl;

char plaintext[256],ciphertext[256];

int static key[256];
cin>>plaintext;




for(i=0;i<256;i++)
{
    cout<<s[i]<<" ";
}
cout<<endl;



cout<<strlen(plaintext);


cout<<endl;
j=0;
int m,n,q;
m=n=0;
for(i=0;i<strlen(plaintext);i++)              //循环产生和明文一样长的key密钥流
{
    int temp;
    m=(m+1)%256;
    n=(n+s[m])%256;

    temp=s[m];
    s[m]=s[n];
    s[n]=temp;

    int q;

    q=(s[i]+s[j])%256;


    key[i]=s[q]; 
    cout<<plaintext[i]<<"(";
    ciphertext[i]=plaintext[i]^key[i];

    cout<<ciphertext[i];


}

cout<<endl;

cout<<"/n密钥流是：";
for(i=0;i<strlen(plaintext);i++)
{   cout<<key[i]<<" "<<plaintext[i];
    cout<<endl;
}


cout<<"密文是：";
for(i=0;i<strlen(plaintext);i++)
{
    cout<<int(ciphertext[i]);
}

cout<<endl;
cout<<"解密后明文为："<<endl;
int a[256];
for(i=0;i<strlen(plaintext);i++)
{
a[i]=ciphertext[i]^key[i];
cout<<a[i];
}

}