P2657 [SCOI2009]windy数

题目描述

windy定义了一种windy数。不含前导零且相邻两个数字之差至少为2的正整数被称为windy数。 windy想知道，

在A和B之间，包括A和B，总共有多少个windy数？

输入输出格式

输入格式：

包含两个整数，A B。

输出格式：

一个整数

输入输出样例

输入样例#1： 

1 10

输出样例#1： 

9

输入样例#2： 

25 50

输出样例#2： 

20

说明

100%的数据，满足 1 <= A <= B <= 2000000000 。

Solution：

　　本题显然数位$DP$，暂时不会（留着填坑～）。

　　提供打表的思路，先线下每$10^6$个处理一次，统计出$2000$个答案（前缀和$sum[i]$表示$1$到$i*10^6$中满足条件的个数）。

　　那么查询时就直接瞎搞模拟，最多计算$10^6$次。

打表代码：

/**************************************************************
    Problem: 1026
    User: five20
    Language: C++
    Result: Accepted
    Time:256 ms
    Memory:1296 kb
****************************************************************/
 
#include<iostream>
#include<cstdio>
#include<algorithm>
#include<cmath>
#define For(i,a,b) for(int (i)=(a);(i)<=(b);(i)++)
using namespace std;
const int N=1e6+5;
int ans,a,b,sum[2005]={0, 202174, 136131, 138503, 138214, 138252, 138252, 138214, 138503, 136131, 155315, 0, 0, 0, 138214, 138252, 138252, 138214, 138503, 136131, 155315, 155315, 0, 0, 0, 138252, 138252, 138214, 138503, 136131, 155315, 155315, 136131, 0, 0, 0, 138252, 138214, 138503, 136131, 155315, 155315, 136131, 138503, 0, 0, 0, 138214, 138503, 136131, 155315, 155315, 136131, 138503, 138214, 0, 0, 0, 138503, 136131, 155315, 155315, 136131, 138503, 138214, 138252, 0, 0, 0, 136131, 155315, 155315, 136131, 138503, 138214, 138252, 138252, 0, 0, 0, 155315, 155315, 136131, 138503, 138214, 138252, 138252, 138214, 0, 0, 0, 155315, 136131, 138503, 138214, 138252, 138252, 138214, 138503, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 155315, 136131, 0, 0, 0, 138252, 138214, 138503, 136131, 155315, 155315, 136131, 138503, 0, 0, 0, 138214, 138503, 136131, 155315, 155315, 136131, 138503, 138214, 0, 0, 0, 138503, 136131, 155315, 155315, 136131, 138503, 138214, 138252, 0, 0, 0, 136131, 155315, 155315, 136131, 138503, 138214, 138252, 138252, 0, 0, 0, 155315, 155315, 136131, 138503, 138214, 138252, 138252, 138214, 0, 0, 0, 155315, 136131, 138503, 138214, 138252, 138252, 138214, 138503, 0, 0, 0, 0, 138503, 138214, 138252, 138252, 138214, 138503, 136131, 155315, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 155315, 136131, 138503, 0, 0, 0, 138214, 138503, 136131, 155315, 155315, 136131, 138503, 138214, 0, 0, 0, 138503, 136131, 155315, 155315, 136131, 138503, 138214, 138252, 0, 0, 0, 136131, 155315, 155315, 136131, 138503, 138214, 138252, 138252, 0, 0, 0, 155315, 155315, 136131, 138503, 138214, 138252, 138252, 138214, 0, 0, 0, 155315, 136131, 138503, 138214, 138252, 138252, 138214, 138503, 0, 0, 0, 0, 138503, 138214, 138252, 138252, 138214, 138503, 136131, 155315, 0, 0, 0, 138214, 138252, 138252, 138214, 138503, 136131, 155315, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 155315, 136131, 138503, 138214, 0, 0, 0, 138503, 136131, 155315, 155315, 136131, 138503, 138214, 138252, 0, 0, 0, 136131, 155315, 155315, 136131, 138503, 138214, 138252, 138252, 0, 0, 0, 155315, 155315, 136131, 138503, 138214, 138252, 138252, 138214, 0, 0, 0, 155315, 136131, 138503, 138214, 138252, 138252, 138214, 138503, 0, 0, 0, 0, 138503, 138214, 138252, 138252, 138214, 138503, 136131, 155315, 0, 0, 0, 138214, 138252, 138252, 138214, 138503, 136131, 155315, 155315, 0, 0, 0, 138252, 138252, 138214, 138503, 136131, 155315, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 155315, 136131, 138503, 138214, 138252, 0, 0, 0, 136131, 155315, 155315, 136131, 138503, 138214, 138252, 138252, 0, 0, 0, 155315, 155315, 136131, 138503, 138214, 138252, 138252, 138214, 0, 0, 0, 155315, 136131, 138503, 138214, 138252, 138252, 138214, 138503, 0, 0, 0, 0, 138503, 138214, 138252, 138252, 138214, 138503, 136131, 155315, 0, 0, 0, 138214, 138252, 138252, 138214, 138503, 136131, 155315, 155315, 0, 0, 0, 138252, 138252, 138214, 138503, 136131, 155315, 155315, 136131, 0, 0, 0, 138252, 138214, 138503, 136131, 155315, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 155315, 136131, 138503, 138214, 138252, 138252, 0, 0, 0, 155315, 155315, 136131, 138503, 138214, 138252, 138252, 138214, 0, 0, 0, 155315, 136131, 138503, 138214, 138252, 138252, 138214, 138503, 0, 0, 0, 0, 138503, 138214, 138252, 138252, 138214, 138503, 136131, 155315, 0, 0, 0, 138214, 138252, 138252, 138214, 138503, 136131, 155315, 155315, 0, 0, 0, 138252, 138252, 138214, 138503, 136131, 155315, 155315, 136131, 0, 0, 0, 138252, 138214, 138503, 136131, 155315, 155315, 136131, 138503, 0, 0, 0, 138214, 138503, 136131, 155315, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 155315, 136131, 138503, 138214, 138252, 138252, 138214, 0, 0, 0, 155315, 136131, 138503, 138214, 138252, 138252, 138214, 138503, 0, 0, 0, 0, 138503, 138214, 138252, 138252, 138214, 138503, 136131, 155315, 0, 0, 0, 138214, 138252, 138252, 138214, 138503, 136131, 155315, 155315, 0, 0, 0, 138252, 138252, 138214, 138503, 136131, 155315, 155315, 136131, 0, 0, 0, 138252, 138214, 138503, 136131, 155315, 155315, 136131, 138503, 0, 0, 0, 138214, 138503, 136131, 155315, 155315, 136131, 138503, 138214, 0, 0, 0, 138503, 136131, 155315, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 155315, 136131, 138503, 138214, 138252, 138252, 138214, 138503, 0, 0, 0, 0, 138503, 138214, 138252, 138252, 138214, 138503, 136131, 155315, 0, 0, 0, 138214, 138252, 138252, 138214, 138503, 136131, 155315, 155315, 0, 0, 0, 138252, 138252, 138214, 138503, 136131, 155315, 155315, 136131, 0, 0, 0, 138252, 138214, 138503, 136131, 155315, 155315, 136131, 138503, 0, 0, 0, 138214, 138503, 136131, 155315, 155315, 136131, 138503, 138214, 0, 0, 0, 138503, 136131, 155315, 155315, 136131, 138503, 138214, 138252, 0, 0, 0, 136131, 155315, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 138503, 138214, 138252, 138252, 138214, 138503, 136131, 155315, 0, 0, 0, 138214, 138252, 138252, 138214, 138503, 136131, 155315, 155315, 0, 0, 0, 138252, 138252, 138214, 138503, 136131, 155315, 155315, 136131, 0, 0, 0, 138252, 138214, 138503, 136131, 155315, 155315, 136131, 138503, 0, 0, 0, 138214, 138503, 136131, 155315, 155315, 136131, 138503, 138214, 0, 0, 0, 138503, 136131, 155315, 155315, 136131, 138503, 138214, 138252, 0, 0, 0, 136131, 155315, 155315, 136131, 138503, 138214, 138252, 138252, 0, 0, 0, 155315, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 138503, 138214, 138252, 138252, 138214, 138503, 136131, 155315, 0, 0, 0, 138214, 138252, 138252, 138214, 138503, 136131, 155315, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 155315, 136131, 138503, 138214, 0, 0, 0, 138503, 136131, 155315, 155315, 136131, 138503, 138214, 138252, 0, 0, 0, 136131, 155315, 155315, 136131, 138503, 138214, 138252, 138252, 0, 0, 0, 155315, 155315, 136131, 138503, 138214, 138252, 138252, 138214, 0, 0, 0, 155315, 136131, 138503, 138214, 138252, 138252, 138214, 138503, 0, 0, 0, 0, 138503, 138214, 138252, 138252, 138214, 138503, 136131, 155315, 0, 0, 0, 138214, 138252, 138252, 138214, 138503, 136131, 155315, 155315, 0, 0, 0, 138252, 138252, 138214, 138503, 136131, 155315, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 155315, 136131, 138503, 138214, 138252, 0, 0, 0, 136131, 155315, 155315, 136131, 138503, 138214, 138252, 138252, 0, 0, 0, 155315, 155315, 136131, 138503, 138214, 138252, 138252, 138214, 0, 0, 0, 155315, 136131, 138503, 138214, 138252, 138252, 138214, 138503, 0, 0, 0, 0, 138503, 138214, 138252, 138252, 138214, 138503, 136131, 155315, 0, 0, 0, 138214, 138252, 138252, 138214, 138503, 136131, 155315, 155315, 0, 0, 0, 138252, 138252, 138214, 138503, 136131, 155315, 155315, 136131, 0, 0, 0, 138252, 138214, 138503, 136131, 155315, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 155315, 136131, 138503, 138214, 138252, 138252, 0, 0, 0, 155315, 155315, 136131, 138503, 138214, 138252, 138252, 138214, 0, 0, 0, 155315, 136131, 138503, 138214, 138252, 138252, 138214, 138503, 0, 0, 0, 0, 138503, 138214, 138252, 138252, 138214, 138503, 136131, 155315, 0, 0, 0, 138214, 138252, 138252, 138214, 138503, 136131, 155315, 155315, 0, 0, 0, 138252, 138252, 138214, 138503, 136131, 155315, 155315, 136131, 0, 0, 0, 138252, 138214, 138503, 136131, 155315, 155315, 136131, 138503, 0, 0, 0, 138214, 138503, 136131, 155315, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 155315, 136131, 138503, 138214, 138252, 138252, 138214, 0, 0, 0, 155315, 136131, 138503, 138214, 138252, 138252, 138214, 138503, 0, 0, 0, 0, 138503, 138214, 138252, 138252, 138214, 138503, 136131, 155315, 0, 0, 0, 138214, 138252, 138252, 138214, 138503, 136131, 155315, 155315, 0, 0, 0, 138252, 138252, 138214, 138503, 136131, 155315, 155315, 136131, 0, 0, 0, 138252, 138214, 138503, 136131, 155315, 155315, 136131, 138503, 0, 0, 0, 138214, 138503, 136131, 155315, 155315, 136131, 138503, 138214, 0, 0, 0, 138503, 136131, 155315, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 155315, 136131, 138503, 138214, 138252, 138252, 138214, 138503, 0, 0, 0, 0, 138503, 138214, 138252, 138252, 138214, 138503, 136131, 155315, 0, 0, 0, 138214, 138252, 138252, 138214, 138503, 136131, 155315, 155315, 0, 0, 0, 138252, 138252, 138214, 138503, 136131, 155315, 155315, 136131, 0, 0, 0, 138252, 138214, 138503, 136131, 155315, 155315, 136131, 138503, 0, 0, 0, 138214, 138503, 136131, 155315, 155315, 136131, 138503, 138214, 0, 0, 0, 138503, 136131, 155315, 155315, 136131, 138503, 138214, 138252, 0, 0, 0, 136131, 155315, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 138503, 138214, 138252, 138252, 138214, 138503, 136131, 155315, 0, 0, 0, 138214, 138252, 138252, 138214, 138503, 136131, 155315, 155315, 0, 0, 0, 138252, 138252, 138214, 138503, 136131, 155315, 155315, 136131, 0, 0, 0, 138252, 138214, 138503, 136131, 155315, 155315, 136131, 138503, 0, 0, 0, 138214, 138503, 136131, 155315, 155315, 136131, 138503, 138214, 0, 0, 0, 138503, 136131, 155315, 155315, 136131, 138503, 138214, 138252, 0, 0, 0, 136131, 155315, 155315, 136131, 138503, 138214, 138252, 138252, 0, 0, 0, 155315, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0};
inline void check(int x){
    if(x<=9){ans++;return;}
    int a=x,b=-5;
    while(a){
        if(abs(a%10-b)<2)return;
        b=a%10;a=a/10;
    }
    ans++;
}
int main(){
    cin>>a>>b;
    if(b-a<=1000000){
        For(i,a,b)check(i);
        cout<<ans;
        return 0;
    }
    int p=ceil(a*1.0/1000000),q=floor(b*1.0/1000000);
    For(i,1,2000)sum[i]+=sum[i-1];
    ans+=sum[q]-sum[p];
    if(!ans)ans++;
    p=p*1000000,q=q*1000000;
    if(a!=p)
    For(i,a,p-1)check(i);
    if(b!=q)
    For(i,q+1,b)check(i);
    cout<<ans;
    return 0;

 

过来填坑啦～：2018-05-26

　　本题套上一个数位$dp$的板子。定义状态$f[i][j]$表示第$i$位为数字$j$时的合法个数。

　　由于本题的约数条件是相邻两位数字之差不小于$2$（且所有个位数均视为满足条件），直接套板子肯定有问题，比如$[45,4500]$，枚举时当前几位连续为$0$时必须往后判断，否则会出兮兮，那么就必须去处理前导$0$的问题。

　　于是在普通的约束上界$limit1$的条件下（即每次枚举数字时是否受限），再加一个$limit2$来判断前导$0$的情况。

　　那么每次枚举当前位数字时，判断一下上一位是否受$limit2$的限制且当前位为$0$，是的话就说明这时存在前导$0$，往后搜索时将$lst$赋值为$-2$（这样$0-(-2)geq 2$）。

　　然后所有的不受限制的情况都记忆化一下，最后前缀和思想相减就是答案了。

$DP$代码：

#include<bits/stdc++.h>
#define il inline
#define ll long long
#define For(i,a,b) for(int (i)=(a);(i)<=(b);(i)++)
using namespace std;
ll a,b,f[20][10],cnt,p[20];
il ll dfs(int pos,int lst,bool limit1,bool limit2){
    if(!pos)return 1;
    if(!limit2&&!limit1&&f[pos][lst]!=-1)return f[pos][lst];
    int op,up=limit1?p[pos]:9;
    ll tmp=0;
    For(i,0,up){
        if(abs(i-lst)<2)continue;
        op=i;
        if(limit2&&!i)op=-2;
        tmp+=dfs(pos-1,op,(limit1)&&(i==up),(op==-2));
    }
    if(!limit1&&!limit2)f[pos][lst]=tmp;
    return tmp;
}
il ll solve(ll x){
    cnt=0;
    while(x)p[++cnt]=x%10,x/=10;
    return dfs(cnt,-2,1,1);
}
int main(){
    cin>>a>>b;
    memset(f,-1,sizeof(f));
    printf("%lld
",solve(b)-solve(a-1));
    return 0;
}