HDU 2187 A sequence of numbers

题目连接  http://acm.hdu.edu.cn/showproblem.php?pid=2817

题意: 给定三个数，判断是等差数列还是等比数列，然后输出第k项.

做法:直接判断即可

#include <iostream>
#include <cstdio>
#include <algorithm>
#include <vector>
#include <set>
#include <queue>
#include <set>
#include <map>
#include <cstring>
#include <functional>
#include <cmath>
typedef unsigned long long ll;
ll mod = 200907;
using namespace std;
ll mul(ll a,ll b){
    return ((a%mod)*(b%mod))%mod;
}
ll pw(ll a,ll n){
    if(n==1)
        return a%mod;
    ll tmp = pw(a,n/2)%mod;
    if(n&1)
        return (tmp*tmp*a)%mod;
    else
        return (tmp*tmp)%mod;

}
int main(){
    ios::sync_with_stdio(0);
    int t;
    cin>>t;
    while(t--){
        ll a,b,c,d;
        cin>>a>>b>>c>>d;
        if(b-a == c-b){
            ll dt = b-a;
            ll ans = a+mul(dt,d-1);
            cout<<ans%mod<<endl;
        }else{
            ll p = b / a;
            ll ans = a*pw(p,d-1);
            cout<<ans%mod<<endl;
        }
    }
}