QOJ.ac
QOJ
ID | Problem | Submitter | Result | Time | Memory | Language | File size | Submit time | Judge time |
---|---|---|---|---|---|---|---|---|---|
#396683 | #6736. Alice and Bob | fangz | TL | 0ms | 0kb | C++14 | 2.0kb | 2024-04-23 01:07:20 | 2024-04-23 01:07:21 |
answer
#include <bits/stdc++.h>
using namespace std;
#define LL long long
#define pb push_back
#define x first
#define y second
#define int long long
#define endl '\n'
const LL maxn = 4e05+7;
const LL N = 1e07+10;
const LL mod = 998244353;
const int inf = 0x3f3f3f3f;
const LL llinf = 5e18;
typedef pair<int,int>pl;
priority_queue<LL , vector<LL>, greater<LL> >mi;//小根堆
priority_queue<LL> ma;//大根堆
LL gcd(LL a, LL b){
return b > 0 ? gcd(b , a % b) : a;
}
LL qpow(LL a , LL b)//快速幂
{
LL sum=1;
while(b){
if(b&1){
sum=sum*a%mod;
}
a=a*a%mod;
b>>=1;
}
return sum;
}
LL f[N] , g[N];
void init(){
f[0] = g[0] = 1;
for(int i=1;i < N; i ++){
f[i]= f[i-1] * i % mod; //计算i的阶乘
g[i] = g[i-1] * qpow(i , mod - 2) % mod; //计算i的乘法逆元 qpow为快速幂
}
}
LL get(int n,int m){ //得到C(n,m)的组合数答案
if(n < m)
return 0;
else
return f[n] * g[m] % mod * g[n-m] % mod;
}
LL lcm(LL a , LL b){
return a / gcd(a , b) * b;
}
int n , m;
vector<int>a(N , 0);
void init(int n){
for(int i = 0 ; i <= n ; i ++){
a[i] = 0;
}
}
void solve()
{
//起步是1 Alice必输
//若Alice能够将比他小的移到第一个,那么Alice赢,否则Alice输
//
cin >> n;
LL ans = f[n - 1];//1开头必输
for(int i = 2 ; i <= n ; i ++){
//1在外面
//共有i - 1个数
int res = n - i;
//从res个数里面选i - 1个数组成排列 -> c(res , i - 1) * f[i - 1] = f[res]
if(i - 1 > res){
break;
}
//[res - 2 , res - 2]
//[res - 4 , res - 3]
//[res - 6 , res - 4]
int add = f[n - i] * g[n - i - i + 1];
add %= mod;
add *= f[n - i];
add %= mod;
ans += add;
// cout << add << endl;
ans %= mod;
}
cout << ans;
}
signed main()
{
ios::sync_with_stdio(false);
cin.tie(0);
cout.tie(0);
cout.precision(10);
int t=1;
init();
// cin>>t;
while(t--)
{
solve();
}
return 0;
}
Details
Tip: Click on the bar to expand more detailed information
Test #1:
score: 0
Time Limit Exceeded
input:
1