Number of Questions in Competition D
#include<cstring>
#include<iostream>
using namespace std;
typedef long long ll;
const ll mod = 998244353;
int n, cnt;
int t;
ll a[150009];
void work()
{
ll ans = 0;
bool f = 0;
for(int i = 1; i <= n; ++i)
{
scanf("%lld", &a[i]);
if(a[i] == cnt && !f)
{
f = 1;
}
else ans += a[i];
}
if(n == 2) cout << ans << endl;
else cout << ans % 11 << endl;
}
int main()
{
while(~scanf("%d %d",&n, &cnt))
work();
return 0;
}
Number of F question combinations
Derivation of Lanzi
#include<bits/stdc++.h>
using namespace std;
#define ll long long
string s[1010];
ll dp[100010];
int mod=998244353;
ll power(ll a,ll b)
{
ll res = 1;
while(b)
{
if(b & 1) res = res * a % mod;
b >>= 1;
a = a * a % mod;
}
return res;
}
int main()
{
dp[4] = 2;
ll n;
//2^(n-2)-或+2*(n/2)+
cin >> n;
/*cout<<((power(2,n-2)+(n%8!=0?-1:1)*power(2,n/2)-(n%8!=0?-1:1)*power(2,n/2-1))%mod+mod)%mod;*/
// 兰子姐姐的写法看不懂
for(int i = 8; i <= n ; i += 4)
{
dp[i] = power(2, i-2) + power(2, i-4) - 4 * dp[i-4];
}
cout << dp[n] << endl;
return 0;
}