BZOJ 1996: [Hnoi2010]chorus 合唱队(dp)

简单的dp题..不能更水了..

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#include<cstdio>#include<cstring>#include<algorithm>#include<iostream>#define rep(i,n) for(int i=0;i<n;++i)#define clr(x,c) memset(x,c,sizeof(x))using namespace std;const int maxn=1000+5;const int mod=19650827;int n;int goal[maxn];int d[maxn][maxn][2];//0放入左,1放入右int dp(int l,int r,int op) { int &ans=d[l][r][op]; if(ans>=0) return ans; ans=0; if(op) { if(goal[l]<goal[r]) ans=dp(l,r-1,0); if(l!=r-1 && goal[r-1]<goal[r]) (ans+=dp(l,r-1,1))%=mod; } else { if(goal[l+1]>goal[l]) ans=dp(l+1,r,0); if(l+1!=r && goal[r]>goal[l]) (ans+=dp(l+1,r,1))%=mod; } return ans%=mod;}int main(){// freopen("test.in","r",stdin);// freopen("test.out","w",stdout); clr(d,-1); scanf("%d",&n); rep(i,n) d[i][i][0]=d[i][i][1]=1; rep(i,n) scanf("%d",&goal[i]); printf("%d\n",(dp(0,n-1,0)+dp(0,n-1,1))%mod); return 0;}

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1996: [Hnoi2010]chorus 合唱队

Time Limit: 4 Sec Memory Limit: 64 MB
Submit: 1045 Solved: 672
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Description

Input

Output

Sample Input

4
1701 1702 1703 1704

Sample Output

8

HINT