2025牛客暑期多校训练营2——Another Day of Sun（01串） · znzryb

## 思路讲解

```cpp
	ll t=binpow(2,tmp,mod),tt=binpow(2,mod-2,mod),tttt=binpow(4,mod-2,mod);
	ll ans=0;
	A[0]=0;
	FOR(i,0,N-1){
		if(A[i]==0 && A[i+1]==1){
			ans+=t;
			ans%=mod;
		}else if(A[i]==-1 && A[i+1]==-1){
			ans+=t*tttt;
			ans%=mod;
		}else if(A[i]==0 && A[i+1]==-1){
			ans+=t*tt;
			ans%=mod;
		}else if(A[i]==-1 && A[i+1]==1){
			ans+=t*tt;
			ans%=mod;
		}
#ifdef LOCAL
    debug(i);debug(ans);
#endif
	}
```

## AC代码

[https://ac.nowcoder.com/acm/contest/view-submission?submissionId=78289781](https://ac.nowcoder.com/acm/contest/view-submission?submissionId=78289781)



::: 源代码

```cpp
// Problem: Another Day of Sun
// Contest: NowCoder
// URL: https://ac.nowcoder.com/acm/contest/108299/A
// Memory Limit: 1024 MB
// Time Limit: 4000 ms
// 
// Powered by CP Editor (https://cpeditor.org)

#include <bits/stdc++.h>
#define all(vec) vec.begin(),vec.end()
#define pb push_back
#define SZ(a) ((int) a.size())
#define FOR(i, a, b) for (int i = (a); i <= (b); ++i)
#define ROF(i, a, b) for (int i = (a); i >= (b); --i)
#define debug(var) cerr << #var <<":"<<var<<"\n";
#define lson(var) (var<<1)
#define rson(var) ((var<<1)+1)
#define V vector

using namespace std;

using  ll = long long;using ull = unsigned long long;
using DB=double;using LD=long double;
// using i128 = __int128;
using pdd = pair<DB,DB>;using plb = pair<ll,bool>;
using pll = pair<ll,ll>;using vll=vector<ll>;
using arr3 = array<ll,3> ;using arr2 = array<ll,2>;
constexpr ll MAXN=static_cast<ll>(5e5)+10,INF=static_cast<ll>(1e17)+9; // 1e18+9也是素数
constexpr ll MAXM=(ll)5e5+10;constexpr ll MAXV=(ll)1e6+10;
constexpr ll mod=998244353;
constexpr double eps=1e-8;const double pi=acos(-1.0);

ll N,M,Q,X,K,T,lT,A[MAXN];
/*

*/
ll binpow(ll a,ll k,const ll &p){	// 迭代快速幂
	ll res=1;
	a%=mod;		// 防止a*a溢出
	while(k>0){
		if((k&1)==1) res=a*res%p;
		a=a*a%p;
		k>>=1;
	}
	return res;
}
inline void __(){
	cin>>N;
	ll cnt=0,tmp=0;
	FOR(i,1,N){
		cin>>A[i];
		if(A[i]==1){
			++cnt;
		}else if(A[i]==-1){
			++tmp;
		}
	}
	ll t=binpow(2,tmp,mod),tt=binpow(2,mod-2,mod),tttt=binpow(4,mod-2,mod);
	ll ans=0;
	A[0]=0;
	FOR(i,0,N-1){
		if(A[i]==0 && A[i+1]==1){
			ans+=t;
			ans%=mod;
		}else if(A[i]==-1 && A[i+1]==-1){
			ans+=t*tttt;
			ans%=mod;
		}else if(A[i]==0 && A[i+1]==-1){
			ans+=t*tt;
			ans%=mod;
		}else if(A[i]==-1 && A[i+1]==1){
			ans+=t*tt;
			ans%=mod;
		}
#ifdef LOCAL
    debug(i);debug(ans);
#endif
	}
	ans%=mod;
	if(ans<0) ans+=mod;
	cout<<ans<<"\n";
}

int main()
{
	ios::sync_with_stdio(false);
	cin.tie(0);
	//cout.tie(0);
	cin>>lT;
	while(lT--)
		__();
	return 0;
}
/*
AC
https://ac.nowcoder.com/acm/contest/view-submission?submissionId=78289781
*/
```


:::


## 心路历程（WA，TLE，MLE……）