Sunday, May 26, 2024

# Codeforces Round #419 (Div. 1), problem: (B) Karen and Test Solution In C/C++

#include <cstdio>
#include <iostream>
#include <cstring>
#include <cstdlib>
using namespace std;
#define ll long long
const int N=200010;
const ll M=1000000007ll;
ll n,a[N],e[N],re[N];
ll suan(ll x,ll y){
ll t=1;while(y){if(y&1)t=t*x%M;x=x*x%M;y>>=1;}return t;
}
ll work(ll x,ll y){
if(y==0)return 1;
return e[x]*re[x-y]%M*re[y]%M;
}
int main(void){
ll i;
scanf(“%I64d”,&n);
e[0]=1;for(i=1;i<=n;i++)e[i]=e[i-1]*i%M;
re[0]=1;for(i=1;i<=n;i++)re[i]=re[i-1]*suan(i,M-2)%M;
for(i=1;i<=n;i++)scanf(“%I64d”,a+i);
if(n==1){cout<<a[1];return 0;}
if(n%2==1){for(i=1;i<n;i++){if(i%2==1)a[i]=(a[i]+a[i+1])%M;else a[i]=(a[i]-a[i+1]+M)%M;}n–;}
ll ans=0;
for(i=n/2;i>=1;i–){
ans=(ans+a[i*2-1]*work(n/2-1,i-1)%M)%M;
if(n%4==0)ans=(ans-a[i*2]*work(n/2-1,i-1)%M+M)%M;
else ans=(ans+a[i*2]*work(n/2-1,i-1)%M+M)%M;
}
cout<<(ans+M)%M;
return 0;
}

## Celebrating Black History Month:...

As February unfolds, so does the annual celebration of...

## The Path to Self-Mastery:...

Embarking on a journey of self-mastery and breaking free...

## Wizards of Waverly Place...

In a spellbinding announcement, Disney has officially revealed that...

## Jim Irsay’s Reported ‘Suspected...

In a shocking turn of events last month, Jim...

Coachella Valley Music and Arts Festival, one of the...

## 2024 Taiwan Election: Pivotal...

As Taiwan gears up for its 2024 presidential election,...

### Celebrating Black History Month: Past, Future

As February unfolds, so does the annual celebration of Black History Month, a time to reflect on the profound contributions, resilience, and rich cultural...

### The Path to Self-Mastery: Lessons from Book ‘The Mountain Is You’

Embarking on a journey of self-mastery and breaking free from self-sabotage is a transformative process that requires dedication and conscious effort. Brianna Wiest's insightful...

### Wizards of Waverly Place Cast Reunites for Enchanting Revival

In a spellbinding announcement, Disney has officially revealed that the beloved fantasy series "Wizards of Waverly Place" is set for a magical comeback, featuring...

### Jim Irsay’s Reported ‘Suspected Overdose’: A Closer Look

In a shocking turn of events last month, Jim Irsay, the owner of the Indianapolis Colts, was reportedly found unresponsive at his home in...

### Coachella 2024: Iconic headliners, unforgettable musical experience!

Coachella Valley Music and Arts Festival, one of the most iconic and eagerly anticipated music festivals globally, has just dropped its highly anticipated lineup...

### 2024 Taiwan Election: Pivotal Moment in Political Landscape

As Taiwan gears up for its 2024 presidential election, the political landscape is buzzing with anticipation and fervor. With the island nation situated at...

### Michael Strahan’s Daughter’s Medulloblastoma Diagnosis

In a recent and heartbreaking revelation, Michael Strahan, former NFL star and television personality, shared the devastating news of his daughter Isabella's diagnosis with...

### Michigan vs. Washington: The 2024 National Championship Clash

In a highly anticipated matchup, the 2024 National Championship will witness a clash of football titans as the Michigan Wolverines square off against the...

### Jason Kelce: Unmasking the Unconventional NFL Icon

In the world of professional football, where conformity often takes center stage, one player stands out as a beacon of individuality, both on and...