```cpp
#include<iostream>
#include<algorithm>
#include<cstdio>
#include<cmath>
using namespace std;
int a[40],n;
int dfs(int x)
{
if(a[x]==0&&a[(x-1+n)%n]==0)return 0;
int t1=a[x],t2=a[(x-1+n)%n];
if(a[x]!=0)
{
for(int i=0;i<t1;i++)
{
a[x]=i;
if(!dfs((x+1)%n))return 1;
a[x]=t1;
}
}
if(a[(x-1+n)%n]!=0)
{
for(int i=0;i<t2;i++)
{
a[(x-1+n)%n]=i;
if(!dfs((x-1+n)%n))return 1;
a[(x-1+n)%n]=t2;
}
}
return 0;
}
int main()
{
cin>>n;
for(int i=0;i<n;i++)cin>>a[i];
if(dfs(0))cout<<"YES\n";
else cout<<"NO\n";
return 0;
}
```
by acmoyjh @ 2019-05-14 21:51:20
希望更丰富的展现？请使用Markdown
by WC自动机 @ 2019-11-11 08:36:36