Little Elephant and Elections小象选举

　　在我正看着roll神的博客的时候发现了自己的错误

#include <cstdio>

#include <cstring>

#include <cmath>

#include <algorithm>

#include <climits>

#include <string>

#include <iostream>

#include <map>

#include <cstdlib>

#include <list>

#include <set>

#include <queue>

#include <stack>

using namespace std;

typedef long long LL;

LL ans;

const LL mod= 1000000007 ;

LL dp[100][100];

LL up[1000];

LL Hash[100];

LL dfs(LL now,LL sum,LL flag)

{

    if(sum>ans) return 0;

    if(now<=0) return sum==ans;

    if(!flag&&~dp[now][sum]) return dp[now][sum];

    LL limit= flag? up[now]:9,ret=0;

    for(LL i = 0;i<= limit;i++){

        if(i==4||i==7) ret+=dfs(now-1,sum+1,flag&&i==limit);

        else ret+=dfs(now-1,sum,flag&&i==limit);

    }

    return flag? ret : dp[now][sum]=ret;

}

LL  solve(LL x)

{

    LL len=0;

    while(x){

        up[++len]=x%10;

        x/=10;

    }

    return dfs(len,0,1);

}



LL len;

LL ans1=0;

void gao(LL dep,LL left,LL w)

{

    w%=mod;

    if(dep==0){

        ans1+=w;ans1%=mod;return ;

    }

    for(LL i= 0;i<=left;i++){

        if(Hash[i])gao(dep-1,left-i,w*Hash[i]--),Hash[i]++;

    }

}

int main()

{

    LL n;

    cin>>n;

    memset(Hash,0,sizeof(Hash));

    for(ans=0 ;ans<10;ans++){

        memset(dp,-1,sizeof(dp));//需要重新初始化。

        Hash[ans]= solve(n) - solve(0);

    }

    len=10;

    while(!Hash[len]) len--;

    for(LL i = 1;i<=len;i++)

        if(Hash[i])gao(6,i-1,Hash[i]);

    cout<<ans1<<endl;

    return 0;

}