牛客多校Round 6

Solved:3

rank:156

J. Heritage of skywalker

学习一下nth_element 可以o (n)的找出前多少大的元素

#include <bits/stdc++.h>
using namespace std;
typedef unsigned long long ull;

int n;
unsigned x, y, z;

unsigned int tang()
{
    unsigned int t;
    x ^= x << 16;
    x ^= x >> 5;
    x ^= x << 1;
    t = x;
    x = y;
    y = z;
    z = t ^ x ^ y;
    return z;
}

ull gcd(ull x, ull y)
{
    if(y == 0) return x;
    return gcd(y, x % y);
}

ull q[10000005];

int main()
{
    int T;
    scanf("%d", &T);
    int cas = 0;
    while(T--)
    {
        cas++;
        cin>>n>>x>>y>>z;
        for(int i = 0; i < n; i++) q[i] = tang();
        
        int len = min(100, n);
        nth_element(q, q + len, q + n, greater<ull>());
        ull ans = 0;
        for(int i = 0; i < len; i++)
        {
            for(int j = i + 1; j < len; j++)
            {
                ull tmp = gcd(q[i], q[j]);
                ans = max(ans, q[i] / tmp * q[j]);
            }
        }
        printf("Case #%d: %llu
", cas, ans);
    }
    return 0;
}