小学四则运算

#include<iostream>
#include<time.h>
#include<stdlib.h>
using namespace std;
void main(){
int t,num,a,n,i,b,k,s,r;
int score=0;
cout<<" "<<endl;
 srand(time(NULL));
for(i=1;i<=30;i++)
{
a=rand()%100;
loop: b=rand()%100;
n=rand()%4;
switch(n)
{
case 0:cout<<""<<i<<""<<endl;
cout<<a<<"+"<<b<<"="; t=a+b;
break;
case 1:cout<<""<<i<<""<<endl;
 cout<<a<<"-"<<b<<"="; t=a-b; break;
case 2:cout<<""<<i<<""<<endl;
 cout<<a<<"*"<<b<<"="; t=-a*b; break;
case 3:cout<<""<<i<<""<<endl;
 cout<<""<<i<<""<<endl;cout<<a<<"/"<<b<<"=";
if(b==0) goto loop; t=a/b; break;}
int cnt=3;
do{
cin>>num;
if(num==t)
{
cout<<"正确"<<endl;}
else
{
if(cnt<3)
cout<<"错误"<<endl;
cout<<"你还有"<<3-cnt<<"次答题机会"<<endl;
++cnt;}
}while(cnt<=3&&num!=t);
if(num!=t)
cout<<"错误！正确答案是:"<<t<<endl;
switch(cnt)
{
case 1:score+=10;break;
case 2:score+=7;break;
case 3:score+=5;break;}
cout<<"当前分数为"<<score<<endl;}
cout<<"最后得分"<<score<<"";}