区间DP，换了数据后WA on #15 #16，显示答案输出了 $0$，求hack。

#include<bits/stdc++.h>
#define ld long double
using namespace std;

namespace LgxTpre
{
	static const int MAX=2010;
	static const int mod=998244353;
	static const int INF=2147483647;
	static const ld  inf=9999999999.0;
	
	int n,k;
	int L,R,op;
	double maxy,now;
	struct point
	{
		ld x,y;
	}a[MAX];
	int pre[MAX][MAX][2];
	double dp[MAX][MAX][2];
	vector<int> ans;
	
	inline double dis(point a,point b)
	{
		return sqrt((a.x-b.x)*(a.x-b.x)+(a.y-b.y)*(a.y-b.y));
	}
	
	inline void mian()
	{
		cin>>n;
		for(int i=1;i<=n;++i)
		{
			cin>>a[i].x>>a[i].y,a[i+n]=a[i];
			if(a[i].y>maxy) maxy=a[i].y,k=i;
		}
		memset(dp,0x7f,sizeof dp);
		dp[k][k][0]=dp[k][k][1]=dp[k+n][k+n][0]=dp[k+n][k+n][1]=0.0;
		for(int len=2;len<=n;++len)
			for(int l=1,r=l+len-1;r<(n<<1);++l,++r)
				if((l<=k&&k<=r)||(l<=k+n&&k+n<=r)) 
				{
					dp[l][r][0]=min(dp[l+1][r][0]+dis(a[l],a[l+1]),dp[l+1][r][1]+dis(a[l],a[r]));
					pre[l][r][0]=dp[l][r][0]==dp[l+1][r][1]+dis(a[l],a[r]);
					dp[l][r][1]=min(dp[l][r-1][1]+dis(a[r-1],a[r]),dp[l][r-1][0]+dis(a[l],a[r]));
					pre[l][r][1]=dp[l][r][1]==dp[l][r-1][1]+dis(a[r-1],a[r]);
				}		
		now=inf;
		for(int i=1;i<=n;++i)	
			for(int j=0;j<=1;++j)
				if(dp[i][i+n-1][j]<now)
					now=dp[i][i+n-1][j],L=i,R=i+n-1,op=j;
		while(L!=R)
		{
			if(op==1) ans.push_back(R),op=pre[L][R][op],--R;
			else ans.push_back(L),op=pre[L][R][op],++L;
		}
		ans.push_back(k); reverse(ans.begin(),ans.end());
		for(int i=0;i<ans.size();++i)
			cout<<(ans[i]>n?ans[i]-n:ans[i])<<" ";
		return;
	}
}

signed main()
{
	ios::sync_with_stdio(false);
	cin.tie(0);
	LgxTpre::mian();
	return (0-0);
}