自己编的代码，但运行之后，总会输出错误，答案对了也是错误，不知道哪出了问题，求高手指点：
#include<iostream>
#include<ctime>
#include<cstdlib>
using namespace std;
int main(){
    int x,y,symbol,ans;
    int n,temp,sum=0;
    srand(time(0));
    for(int i=1;i<=10;i++)
    {
        x=rand()%9+1;
        y=rand()%9+1;
        symbol=rand()%2;
        if(x<y&&symbol==1)
        {
            temp=x;
            x=y;
            y=temp;
        }
    }     switch(symbol)
      {
          case 0:
          ans=x+y;
          cout<<x<<'-'<<y<<'=';break;
      }
      cin>>n;
      if(n==ans)
      {
          sum+=10;
          cout<<"正确"<<endl;
      }
      else
      cout<<"错误"<<endl;
      cout<<"得分:"<<sum<<endl;
      return 0;
      
      
}

这个地方应该是x-y