B. Masha and geometric depression(讨论+暴力)

https://codeforces.com/contest/789/problem/B

---

思路:直接暴力就好。

注意要分清楚0，-1，1的讨论

#include<iostream>
#include<vector>
#include<queue>
#include<cstring>
#include<cmath>
#include<map>
#include<set>
#include<cstdio>
#include<algorithm>
#define debug(a) cout<<#a<<"="<<a<<endl;
using namespace std;
const int maxn=1e5;
typedef long long LL;
inline LL read(){LL x=0,f=1;char ch=getchar();	while (!isdigit(ch)){if (ch=='-') f=-1;ch=getchar();}while (isdigit(ch)){x=x*10+ch-48;ch=getchar();}
return x*f;}
vector<LL>v;
map<LL,LL>map1;
int main(void)
{
  cin.tie(0);std::ios::sync_with_stdio(false);
  LL b1,q,l,m;cin>>b1>>q>>l>>m;
  for(LL i=1;i<=m;i++){
    LL x;cin>>x;
    map1[x]++;
  }
  if(abs(b1)>l) {cout<<"0"<<"\n";return 0;}
  LL temp=b1;
  if(q==1){
    if(map1.count(temp)){
        cout<<"0"<<"\n";
    }
    else cout<<"inf"<<"\n";
  }
  else if(q==-1){
    if(map1.count(temp)&&map1.count(-temp)) cout<<"0"<<"\n";
    else cout<<"inf"<<"\n";
  }
  else if(temp==0||q==0){
    if(temp==0){
        if(map1.count(temp)){
            cout<<"0"<<"\n";
        }
        else cout<<"inf"<<"\n";
    }
    else if(temp!=0&&q==0){
        if(map1.count(0)&&map1.count(temp)) cout<<"0"<<"\n";
        else if(map1.count(0)&&!map1.count(temp)) cout<<"1"<<"\n";
        else if(!map1.count(0)) cout<<"inf"<<"\n";
    }
  }
  else{
    LL sum=0;
    while(abs(temp)<=l){
        if(!map1.count(temp)) sum++;
        temp*=q;
    }
    cout<<sum<<"\n";
  }
return 0;
}