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  • 【uoj】【美团杯2020】平行四边形(原根)

    传送门

    思路:
    满足题目中的条件即为:对于任意相等的(j-i)(y_j-y_i)不相等。
    这里我们构造每个点为((i,g^i))即可。
    那么(displaystyle p_i-p_j=(i-j,g^j(g^{i-j}-1)\% N)),容易发现满足条件。
    代码如下:

    /*
     * Author:  heyuhhh
     * Created Time:  2020/5/19 16:11:42
     */
    #include <iostream>
    #include <algorithm>
    #include <cstring>
    #include <cstdio>
    #include <vector>
    #include <cmath>
    #include <set>
    #include <map>
    #include <queue>
    #include <iomanip>
    #include <assert.h>
    #define MP make_pair
    #define fi first
    #define se second
    #define pb push_back
    #define sz(x) (int)(x).size()
    #define all(x) (x).begin(), (x).end()
    #define INF 0x3f3f3f3f
    #define Local
    #ifdef Local
      #define dbg(args...) do { cout << #args << " -> "; err(args); } while (0)
      void err() { std::cout << std::endl; }
      template<typename T, typename...Args>
      void err(T a, Args...args) { std::cout << a << ' '; err(args...); }
      template <template<typename...> class T, typename t, typename... A> 
      void err(const T <t> &arg, const A&... args) {
      for (auto &v : arg) std::cout << v << ' '; err(args...); }
    #else
      #define dbg(...)
    #endif
    using namespace std;
    typedef long long ll;
    typedef pair<int, int> pii;
    //head
    const int N = 1e3 + 5;
    
    ll qpow(ll a, ll b, ll p) {
        ll ans = 1;
        while(b) {
            if(b & 1) ans = ans * a % p;
            a = a * a % p;
            b >>= 1;
        }
        return ans;
    }
    //求模m的原根
    int work(ll P, ll m) {   //P = phi(m)
        vector <int> div;
        ll x = P;
        for(int i = 2; 1ll * i * i <= x; i++) {
            if(x % i == 0) {
                div.push_back(i);
                while(x % i == 0) x /= i;
            }
        }
        if(x > 1) div.push_back(x);
        for(int i = 2;; i++) {
            bool ok = true;
            for(auto x : div) {
                if(qpow(i, P / x, m) == 1) {
                    ok = false; break;
                }
            }
            if(ok) return i;
        }
        return -1;
    } 
    
    void run() {
        int n;
        cin >> n;
        int g = work(n, n + 1);
        if (g == -1) {
            cout << -1 << '
    ';
            return;
        }
        for (int i = 1; i <= n; i++) {
            cout << i << ' ' << qpow(g, i, n + 1) << '
    ';
        }
    }
    
    int main() {
        ios::sync_with_stdio(false);
        cin.tie(0); cout.tie(0);
        cout << fixed << setprecision(20);
        int T; cin >> T; while(T--)
        run();
        return 0;
    }
    
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  • 原文地址:https://www.cnblogs.com/heyuhhh/p/12964903.html
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