CERC2017 F: Faulty Factorial 简单数论题

 #include  <iostream>
 using namespace std;
 #define ll long long
 const int N  = ;
 ll n,p,r;
 ll poww(ll a,ll b){
     ll ans  =1ll;
     while(b){
         if(b&) ans =ans*a%p;
         b>>=;
         a=a*a%p;
     }
     return ans%p;
 }
 int  main()
 {
     //每次都要注意-1 -1的情况
     scanf("%lld%lld%lld",&n,&p,&r);
     if(n>=*p){
         if(r==){
             printf("%lld 1\n",p+);
         }
          else{
              printf("-1 -1\n");
          }
     }
     else if(n>=p){
         if(r==){
             int flag =;
             for(ll i=;i<=n;i++){
                 if(i!=p)//起初if的{}写错了
                 {
                 printf("%lld 1\n",i);
                 flag =;
                 break;
                 }
             }
             if(!flag)printf("-1 -1\n"); //n=p=2
         }
         else{
             ll ans=1ll;
             for(ll i=;i<=n;i++) {
                 if(i!=p) ans =ans*i%p;
             }
             int  flag =;
             for(ll i=;i<p;i++){
                 if(ans*i%p==r) {
                     printf("%lld %lld\n",p,i);
                     flag =;
                     break;
                 }
             }
             if(flag==) printf("-1 -1\n");
         }
     }
     else{
         ll ans =1ll;
         for(ll i=;i<=n;i++) ans =ans*i%p;
         int  flag =;
         ans = poww(ans,p-);//放到里面会超时
         for(ll i=;i<=n;i++){
             ll x= r*i%p*ans%p;
             // ans/i*x%p==r
             // x=r*i%p/ans%p;
             if(x>=&&x<i){
                 printf("%lld %lld\n",i,x);
                 flag =;
                 break;
             }
         }
         if(!flag) printf("-1 -1\n");
     }
     return ;

 }