[2018 ACM-ICPC 焦作赛区网络赛] G - Give Candies （欧拉降幂）

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[2018 ACM-ICPC 焦作赛区网络赛] G - Give Candies

求  ： 2 ^ (n-1)

利用欧拉降幂公式：

(a^b)%m=a^(b%phi(m))%m

#include<bits/stdc++.h>
using namespace std;
#define clr(a) memset(a,0,sizeof(a))
#define line cout<<"----------"<<endl

typedef long long ll;
const int maxn = 1e5 + 10;
const int MAXN = 1e6 + 10;
const int INF = 0x3f3f3f3f;
const int MOD = 1e9 + 7;
const int N = 1010;

ll qkm(ll a, ll b, ll c = MOD){
    ll s = 1; a %= c;
    while(b){
        if(b & 1)
            s = s * 1ll * a % c;
        b >>= 1;
        a = a * 1ll * a % c;
    }
    return s;
}

int main(){
    int T;
    cin >> T;
    while(T--){
        string s;
        cin >> s;
        ll ans = 0;
        for(ll i=0; s[i]; i++){
            ans = ans * 10 + (s[i] - '0');
            ans %= (MOD - 1);
        }
        ans = (ans - 1 + MOD -1) % (MOD - 1);//防止负数
        ll cnt = qkm(2, ans-1, MOD);

        printf("%lld\n", cnt);
    }
    return 0;
}