ARC114

A
\(\quad\)直接状压就过了。。。

code

#include<iostream>
#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<string>
#include<algorithm>
#include<cmath>
#include<ctime>
#include<climits>
#include<sstream>
#include<fstream>
using namespace std;
#define int long long

const int N = 51;

bool book[N];
int p[N] , tot;

inline void build()
{
    book[0] = book[1] = 1;
    int n = 50;
    for(register int i = 2 ; i <= n ; i++)
    {
        if(book[i] == 0)
        {
            tot++;
            p[tot] = i;
        }
        for(register int j = 1 ; j <= tot && p[j] * i <= n ; j++)
        {
            book[p[j] * i] = 1;
            if(i % p[j] == 0)
            {
                break;
            }
        }
    }
}

int x[N];

inline int gcd(int a , int b)
{
    if(b == 0)
    {
        return a;
    }
    else
    {
        return gcd(b , a % b);
    }
}

signed main()
{
    ios::sync_with_stdio(false);
    int n;
    cin >> n;
    build();
    for(register int i = 1 ; i <= n ; i++)
    {
        cin >> x[i];
    }
    int ans = INT64_MAX;
    for(register int S = 0 ; S < (1 << tot) ; S++)
    {
        int res = 1;
        for(register int i = 0 ; i < tot ; i++)
        {
            if((S >> i) & 1)
            {
                res *= p[i + 1];
            }
        }
        bool zzz = 1;
        for(register int i = 1 ; i <= n ; i++)
        {
            if(gcd(x[i] , res) == 1)
            {
                zzz = 0;
                break;
            }
        }
        if(zzz)
        {
            ans = min(ans , res);
        }
    }
    cout << ans;
    return 0;
}

B
\(\quad\)找环就好了。

code

#include<iostream>
#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<string>
#include<algorithm>
#include<cmath>
#include<ctime>
#include<climits>
#include<sstream>
#include<fstream>
using namespace std;
#define int long long

const int N = 2e5 + 10;
const int Mod = 998244353;

int f[N];

int head[N] , net[N] , vis[N];
int tot = 1;

inline void add(int u , int v)
{
    tot++;
    net[tot] = head[u];
    head[u] = tot;
    vis[tot] = v;
}

int num = 0;

int col[N] , cl;

inline void dfs(int u)
{
    col[u] = cl;
    for(register int i = head[u] ; i ; i = net[i])
    {
        int v = vis[i];
        if(col[v] == cl)
        {
            num++;
            return;
        }
        if(col[v] != 0)
        {
            return;
        }
        dfs(v);
    }
}

inline int pow(int a , int b , int c)
{
    int ans = 1;
    while(b)
    {
        if(b & 1)
        {
            ans *= a;
            ans %= c;
        }
        a *= a;
        a %= c;
        b >>= 1;
    }
    return ans;
}

signed main()
{
    ios::sync_with_stdio(false);
    int n;
    cin >> n;
    for(register int i = 1 ; i <= n ; i++)
    {
        cin >> f[i];
        add(i , f[i]);
    }
    for(register int i = 1 ; i <= n ; i++)
    {
        if(col[i] == 0)
        {
            cl++;
            dfs(i);
        }
    }
    cout << ((pow(2 , num , Mod) - 1) % Mod + Mod) % Mod;
    return 0;
}

后面的GGG了。