codeforces613E

Puzzle Lover

Oleg Petrov loves crossword puzzles and every Thursday he buys his favorite magazine with crosswords and other word puzzles. In the last magazine Oleg found a curious puzzle, and the magazine promised a valuable prize for it's solution. We give a formal description of the problem below.

The puzzle field consists of two rows, each row contains n cells. Each cell contains exactly one small English letter. You also are given a word w, which consists of ksmall English letters. A solution of the puzzle is a sequence of field cells c₁, ..., c_k, such that:

For all i from 1 to k the letter written in the cell c_i matches the letter w_i;
All the cells in the sequence are pairwise distinct;
For all i from 1 to k - 1 cells c_i and c_i + 1 have a common side.

Oleg Petrov quickly found a solution for the puzzle. Now he wonders, how many distinct solutions are there for this puzzle. Oleg Petrov doesn't like too large numbers, so calculate the answer modulo 10⁹ + 7.

Two solutions c_i and c'_i are considered distinct if the sequences of cells do not match in at least one position, that is there is such j in range from 1 to k, such that c_j ≠ c'_j.

Input

The first two lines contain the state of the field for the puzzle. Each of these non-empty lines contains exactly n small English letters.

The next line is left empty.

The next line is non-empty and contains word w, consisting of small English letters.

The length of each line doesn't exceed 2 000.

Output

Print a single integer — the number of distinct solutions for the puzzle modulo 10⁹ + 7.

Examples

Input

code
edoc

code

Output

Input

aaa
aaa

aa

Output

14

sol：超好的一道dp题

事实上我代码和上面略有不同
提醒一下：注意一点就是不要算重，比如要向左或向右绕一圈回来的时候一圈的长度最小值为4，因为直接往下走的话在中间那段的转移中已经算过了

#include <bits/stdc++.h>

using namespace std;

typedef long long ll;

inline ll read()

{

    ll s=;

    bool f=;

    char ch=' ';

    while(!isdigit(ch))

    {

        f|=(ch=='-'); ch=getchar();

    }

    while(isdigit(ch))

    {

        s=(s<<)+(s<<)+(ch^); ch=getchar();

    }

    return (f)?(-s):(s);

}

#define R(x) x=read()

inline void write(ll x)

{

    if(x<)

    {

        putchar('-'); x=-x;

    }

    if(x<)

    {

        putchar(x+''); return;

    }

    write(x/);

    putchar((x%)+'');

    return;

}

#define W(x) write(x),putchar(' ')

#define Wl(x) write(x),putchar('\n')

const int N=;

const ll Base=,Mod=;

int n,Len;

char S[][N],T[N];

inline void Ad(ll &x,ll y)

{

    x+=y; x-=(x>=Mod)?Mod:;

}

ll Seed[N];

inline void Prepare(int n)

{

    int i; Seed[]=;

    for(i=;i<=n;i++) Seed[i]=1ll*Seed[i-]*Base%Mod;

}

struct Hash

{

    ll Hash[N];

    inline void Make(int n,char *S)

    {

        int i; Hash[]=; for(i=;i<=n;i++) Hash[i]=(Hash[i-]*Base%Mod+(S[i]-'a'+))%Mod;

    }

    inline ll Ask(int l,int r)

    {

        return (ll)(Hash[r]+Mod-Hash[l-]*Seed[r-l+]%Mod)%Mod;

    }

}Pre[],Suf[],HT;

ll dp[][N][N];

//dp[i][j][k]表示在第i行,第j-1个(即i,j在当前点右边),已经匹配了k为的方案数

inline ll Solve(bool opt)

{

    ll res=;

    int i,j,k;

    memset(dp,,sizeof dp);

    for(j=;j<=n;j++)

    {

        dp[][j][]=dp[][j][]=;

        for(i=;i<=;i++) for(k=;k<=min(n-j+,Len/);k++) //向右绕一圈回来

        {

            if(Pre[i].Ask(j,j+k-)==HT.Ask(Len-*k+,Len-k)&&Suf[i^].Ask(n-(j+k-)+,n-j+)==HT.Ask(Len-k+,Len))

            {

                if((k*!=Len)||opt) Ad(res,dp[i][j][Len-k*]);

            }

        }

        for(i=;i<=;i++) for(k=;k<=min(j,Len/);k++) //向左绕一圈回来

        {

            if(Suf[i].Ask(n-j+,n-(j-k+)+)==HT.Ask(,k)&&Pre[i^].Ask(j-k+,j)==HT.Ask(k+,k*))

            {

                if((k*!=Len)||opt) Ad(dp[i^][j+][k*],);

            }

        }

        for(i=;i<=;i++) for(k=;k<=Len;k++)

        {

            if(T[k]==S[i][j])

            {

                Ad(dp[i][j+][k],dp[i][j][k-]);

                if(k<Len&&T[k+]==S[i^][j])

                {

                    Ad(dp[i^][j+][k+],dp[i][j][k-]);

                }

            }

        }

        for(i=;i<=;i++) Ad(res,dp[i][j+][Len]);

    }

    return res;

}

int main()

{

    ll i,j,ans=;

    Prepare();

    scanf("%s",S[]+); n=strlen(S[]+); scanf("%s",S[]+); scanf("%s",T+); Len=strlen(T+);

    for(i=;i<=;i++)

    {

        Pre[i].Make(n,S[i]); reverse(S[i]+,S[i]+n+); Suf[i].Make(n,S[i]); reverse(S[i]+,S[i]+n+);

    }

    HT.Make(Len,T);

    Ad(ans,Solve());

    if(Len>)

    {

        reverse(T+,T+Len+); HT.Make(Len,T); Ad(ans,Solve());

    }

    if(Len==)

    {

        for(j=;j<=n;j++) for(i=;i<=;i++) if(S[i][j]==T[]&&S[i^][j]==T[]) Ad(ans,Mod-);

    }

    Wl(ans);

    return ;

}

/*

input

code

edoc

code

output

4

input

aaa

aaa

aa

output

14

input

v

s

sv

output

1

*/

巴特西

codeforces613E

Puzzle Lover

最新文章

热门文章