链接:https://www.nowcoder.com/acm/contest/144/J
来源:牛客网
skywalkert, the new legend of Beihang University ACM-ICPC Team, retired this year leaving a group of newbies again.
To prove you have at least 0.1% IQ of skywalkert, you have to solve the following problem:
Given n positive integers, for all (i, j) where 1 ≤ i, j ≤ n and i ≠ j, output the maximum value among
.
means the Lowest Common Multiple.
Rumor has it that he left a heritage when he left, and only the one who has at least 0.1% IQ(Intelligence Quotient) of his can obtain it.
To prove you have at least 0.1% IQ of skywalkert, you have to solve the following problem:
Given n positive integers, for all (i, j) where 1 ≤ i, j ≤ n and i ≠ j, output the maximum value among
输入描述:
The input starts with one line containing exactly one integer t which is the number of test cases. (1 ≤ t ≤ 50)
For each test case, the first line contains four integers n, A, B, C. (2 ≤ n ≤ 10
7
, A, B, C are randomly selected in unsigned 32 bits integer range)
The n integers are obtained by calling the following function n times, the i-th result of which is ai, and we ensure all ai > 0. Please notice that for each test case x, y and z should be reset before being called.
No more than 5 cases have n greater than 2 x 10
6
.
输出描述:
For each test case, output "Case #x: y" in one line (without quotes), where x is the test case number (starting from 1) and y is the maximum lcm.
示例1
输出
复制Case #1: 68516050958 Case #2: 5751374352923604426
分析:由于数据看上去像是随机⽣成的,只需要选出前 100 ⼤的数平⽅暴⼒即可。 随机两个正整数互质的概率为 6/π。
比赛的时候想到应该是枚举前面最大的多少项,但是因为不知道怎么快速计算前面多少项没有试一发了!!
结束后补题知道了nth_element求数组中最大的前多少项
AC代码:
#include <map> #include <set> #include <stack> #include <cmath> #include <queue> #include <cstdio> #include <vector> #include <string> #include <bitset> #include <cstring> #include <iomanip> #include <iostream> #include <algorithm> #define ls (r<<1) #define rs (r<<1|1) #define debug(a) cout << #a << " " << a << endl using namespace std; typedef unsigned long long ll; const ll maxn = 1e7+10; const ll mod = 998244353; unsigned x, y, z, a[maxn]; ll n; unsigned gcd( unsigned a, unsigned b ) { if( a == 0 ) { return b; } else if( b == 0 ) { return a; } else { return gcd( b, a%b ); } } unsigned rnd() { unsigned t; x ^= x << 16; x ^= x >> 5; x ^= x << 1; t = x; x = y; y = z; z = t ^ x ^ y; return z; } int main() { ios::sync_with_stdio(0),cin.tie(0),cout.tie(0); ll T, t = 1; scanf("%llu",&T); while( T -- ) { scanf("%llu%u%u%u",&n,&x,&y,&z); for( ll i = 0; i < n; i ++ ) { a[i] = rnd(); } ll m = min( (ll)n, (ll)100 ); nth_element( a, a+n-m, a+n ); ll ans = 0; for( ll i = n-m; i < n; i ++ ) { for( ll j = i+1; j < n; j ++ ) { ans = max( ans, (ll)a[i]*a[j]/gcd(a[i],a[j]) ); } } printf("Case #%llu: %llu\n", t++, ans); } return 0; }