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;

        }

    }

}