剪气球串

#include <bits/stdc++.h>
using namespace std;

#define maxn 100009
const int MOD = 1e9 + 7;
int main()
{
    int n;
    int a[maxn];
    int dp[maxn];
    int cnt[11];
    
    while (~scanf("%d",&n))
    {
        memset(a,0,sizeof(a));
        memset(dp,0,sizeof(dp));
        for (int i = 1;i<=n;i++)
        {
            scanf("%d",&a[i]);
        }
        dp[0] = 1;
        for (int i = 1;i<=n;i++)
        {
            memset(cnt,0,sizeof(cnt));
            for (int j = 0;j<i;j++)
            {
                cnt[a[i-j]]++;
                if (cnt[a[i-j]] > 1)
                {
                    break;
                }
                dp[i] = (dp[i] + dp[i-j-1])%MOD;
            }
        }
        printf("%d\n",dp[n]);
    }
    return 0;
}