P2657 [SCOI2009]windy数

#include<cstdio>
#include<iostream>
#include<cstring>
#include<algorithm>
#include<cmath>

using namespace std;

int dp[20][20],num[20];

inline int dfs(int now,int pre,bool limit)
{
    if(now==0) return 1;
    if(dp[now][pre]!=-1&&!limit) return dp[now][pre];
    int ans=0,up=9;
    if(limit) up=num[now];
    for(register int i=0;i<=up;++i)
    {
        if((abs(i-pre))<2) continue;
        if(i==0&&pre==-10) ans+=dfs(now-1,-10,limit&&(i==num[now]));
        else ans+=dfs(now-1,i,limit&&(i==num[now]));
    }
    if(!limit) dp[now][pre]=ans;
    return ans;
}

inline int solve(int k)
{
    memset(dp,-1,sizeof(dp));
    int pos=0;
    while(k>0)
    {
        num[++pos]=k%10;
        k/=10;
    }
    return dfs(pos,-10,true);
}

int main()
{
    int x,y;
    scanf("%d%d",&x,&y);
    printf("%d\n",solve(y)-solve(x-1));
    return 0;
}