求问代码的逻辑错误

#include<iostream>
using namespace std;
int main()
{int score[10],i(0),j(0);
cout<<"请输入十位同学的成绩";
for(;i<=9;i++)
{cin>>score[i];
if(score[i]>=0&&score[i]<60) score[i]=1;
else if(score[i]>=60&&score[i]<80) score[i]=2;
else if(score[i]>=80&&score[i]<90) score[i]=3;
else if(score[i]>=90&&score[i]<=100) score[i]=4;}
do {switch(score[j])
{case1:{j++;cout<<"D"<<endl;break;}
case2:{j++;cout<<"C"<<endl;break;}
case3:{j++;cout<<"B"<<endl;break;}
case4:{j++;cout<<"A"<<endl;break;}
default: {cout<<"错误，请重新输入";break;}}}
while(j<9);
return 0;
}