bzoj 2173 整数的lqp拆分 | dp | 找规律

这道题样例解释似乎有问题？f[1]=1 f[2]=1 f[3]=2
3=1+1+1 ->1*1*1=13=1+2->1*1=13=2+1->1*1=13=3->2=2为此纠结了好久…… 得出方程 dp[i]=sigma(dp[j]*f[i-j])

[code]#include<cstdio>

#include<cstdlib>

#include<cstring>

#include<algorithm>

#include<cmath>

#define md 1000000007

#define ll long long

#define inf (int) 1e9

#define eps 1e-8

#define N 1000010

using

namespace

std;

ll f
;

int

main()

{

int

n;

scanf

(

"%d"

,&n);

f[0]=0; f[1]=1;

for

(

int

i=2;i<=n;i++) f[i]=(2*f[i-1]+f[i-2])%md;

printf

(

"%lld\n"

,f
);

return

0;

}