大神勿喷

#include<iostream>
#include<ctime>
#include<cstdlib>
#include<string>
using namespace std;
int main(void)
    {
    int n,num,count=1,i=10,u=0;
    string mystring;
    cout<<"选择难度："<<"easy,hard,very hard,impossible"<<"\n" ;
    cin>>mystring;
    if(mystring == "easy")
    num=rand()%100;
    if(mystring == "hard");
    num=rand()%1000;
    if(mystring == "very hard")
    num=rand()%5000;
    if(mystring == "impossible")
    {
    num=rand()%10000;
    for(i=10;i>0;u++,i--)
        {
            cout<<"猜一个数"<<"\n"<<"还剩"<<i<<"次机会。"<<"\n";
            cin>>n;
            if(n == num)
                break;
            else if(n>num)
            cout<<"大了！"<<"\n"<<"还剩"<<i<<"次机会！"<<"\n"<<"\n"<<"\n";
            else
            cout<<"小了！"<<"\n"<<"还剩"<<i<<"此机会！"<<"\n"<<"\n"<<"\n";   
        }
    cout<<"挑战成功！！！"<<"用了"<<u<<"次机会！";
    return 0;
    }
    do
    {
    cout<<"猜一个数：";
    cin>>n;
    if(n == num)
    break;
    else if(n>num)
    cout<<"大了！"<<endl;
    else
    cout<<"小了！"<<endl;
    count++;
    }while(true);
    cout<<"历经"<<count<<"次，猜对了。"<<endl;
    return 0;
}