「SCOI2009」windy数

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分块打表大法好！打表万岁！dalao保佑我打表进省队！（逃

传送门

洛谷P2657

BZOJ1026

题解

很显然，这题正解是数位DP，但是我觉得上分块打表会更好玩一些！

设块大为$S$，我们可以先写一个暴力，计算出S、2S、3S、4S……内一共有多少个windy数，把这个表事先打出来。由于$A、B$都比较小，打这个表不会用很长时间。蒟蒻我的机子还不错，八框框的i5 CPU，最高可以睿频到3.4GHz，用了四十多秒就跑完了。然后根据容斥原理，最后的答案是$Solve(B)-Solve(A-1)$，其中$Solve(x)$用于求解共有多少个windy数$\in[1,x]$。且必有$x \in [kS,(k+1)S]$。$Solve(kS)$已经事先打过表了，暴力枚举并检验$[kS+1,x]$中有多少个windy数即可。为了减少最终代码长度，令$S=10^6$或$10^7​$即可。

代码

还好，不是很长呢poi。

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#include<cstdio>
using namespace std;
const int table[2005]={0,202174,338305,476808,615022,753274,891526,1029740,1168243,1304374,1459689,1459689,1459689,1459689,1597903,1736155,1874407,2012621,2151124,2287255,2442570,2597885,2597885,2597885,2597885,2736137,2874389,3012603,3151106,3287237,3442552,3597867,3733998,3733998,3733998,3733998,3872250,4010464,4148967,4285098,4440413,4595728,4731859,4870362,4870362,4870362,4870362,5008576,5147079,5283210,5438525,5593840,5729971,5868474,6006688,6006688,6006688,6006688,6145191,6281322,6436637,6591952,6728083,6866586,7004800,7143052,7143052,7143052,7143052,7279183,7434498,7589813,7725944,7864447,8002661,8140913,8279165,8279165,8279165,8279165,8434480,8589795,8725926,8864429,9002643,9140895,9279147,9417361,9417361,9417361,9417361,9572676,9708807,9847310,9985524,10123776,10262028,10400242,10538745,10538745,10538745,10538745,10538745,10538745,10538745,10538745,10538745,10538745,10538745,10538745,10538745,10538745,10538745,10538745,10538745,10538745,10538745,10538745,10538745,10538745,10538745,10538745,10538745,10538745,10538745,10538745,10538745,10538745,10538745,10538745,10538745,10694060,10830191,10830191,10830191,10830191,10968443,11106657,11245160,11381291,11536606,11691921,11828052,11966555,11966555,11966555,11966555,12104769,12243272,12379403,12534718,12690033,12826164,12964667,13102881,13102881,13102881,13102881,13241384,13377515,13532830,13688145,13824276,13962779,14100993,14239245,14239245,14239245,14239245,14375376,14530691,14686006,14822137,14960640,15098854,15237106,15375358,15375358,15375358,15375358,15530673,15685988,15822119,15960622,16098836,16237088,16375340,16513554,16513554,16513554,16513554,16668869,16805000,16943503,17081717,17219969,17358221,17496435,17634938,17634938,17634938,17634938,17634938,17773441,17911655,18049907,18188159,18326373,18464876,18601007,18756322,18756322,18756322,18756322,18756322,18756322,18756322,18756322,18756322,18756322,18756322,18756322,18756322,18756322,18756322,18756322,18756322,18756322,18756322,18756322,18756322,18756322,18756322,18756322,18756322,18756322,18756322,18756322,18756322,18756322,18756322,18911637,19047768,19186271,19186271,19186271,19186271,19324485,19462988,19599119,19754434,19909749,20045880,20184383,20322597,20322597,20322597,20322597,20461100,20597231,20752546,20907861,21043992,21182495,21320709,21458961,21458961,21458961,21458961,21595092,21750407,21905722,22041853,22180356,22318570,22456822,22595074,22595074,22595074,22595074,22750389,22905704,23041835,23180338,23318552,23456804,23595056,23733270,23733270,23733270,23733270,23888585,24024716,24163219,24301433,24439685,24577937,24716151,24854654,24854654,24854654,24854654,24854654,24993157,25131371,25269623,25407875,25546089,25684592,25820723,25976038,25976038,25976038,25976038,26114252,26252504,26390756,26528970,26667473,26803604,26958919,26958919,26958919,26958919,26958919,26958919,26958919,26958919,26958919,26958919,26958919,26958919,26958919,26958919,26958919,26958919,26958919,26958919,26958919,26958919,26958919,26958919,26958919,26958919,26958919,26958919,26958919,26958919,26958919,26958919,26958919,27114234,27250365,27388868,27527082,27527082,27527082,27527082,27665585,27801716,27957031,28112346,28248477,28386980,28525194,28663446,28663446,28663446,28663446,28799577,28954892,29110207,29246338,29384841,29523055,29661307,29799559,29799559,29799559,29799559,29954874,30110189,30246320,30384823,30523037,30661289,30799541,30937755,30937755,30937755,30937755,31093070,31229201,31367704,31505918,31644170,31782422,31920636,32059139,32059139,32059139,32059139,32059139,32197642,32335856,32474108,32612360,32750574,32889077,33025208,33180523,33180523,33180523,33180523,33318737,33456989,33595241,33733455,33871958,34008089,34163404,34318719,34318719,34318719,34318719,34456971,34595223,34733437,34871940,35008071,35163386,35163386,35163386,35163386,35163386,35163386,35163386,35163386,35163386,35163386,35163386,35163386,35163386,35163386,35163386,35163386,35163386,35163386,35163386,35163386,35163386,35163386,35163386,35163386,35163386,35163386,35163386,35163386,35163386,35163386,35163386,35318701,35454832,35593335,35731549,35869801,35869801,35869801,35869801,36005932,36161247,36316562,36452693,36591196,36729410,36867662,37005914,37005914,37005914,37005914,37161229,37316544,37452675,37591178,37729392,37867644,38005896,38144110,38144110,38144110,38144110,38299425,38435556,38574059,38712273,38850525,38988777,39126991,39265494,39265494,39265494,39265494,39265494,39403997,39542211,39680463,39818715,39956929,40095432,40231563,40386878,40386878,40386878,40386878,40525092,40663344,40801596,40939810,41078313,41214444,41369759,41525074,41525074,41525074,41525074,41663326,41801578,41939792,42078295,42214426,42369741,42525056,42661187,42661187,42661187,42661187,42799439,42937653,43076156,43212287,43367602,43367602,43367602,43367602,43367602,43367602,43367602,43367602,43367602,43367602,43367602,43367602,43367602,43367602,43367602,43367602,43367602,43367602,43367602,43367602,43367602,43367602,43367602,43367602,43367602,43367602,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int A,B;
inline int read()
{
	int ret=0,f=1;char ch=getchar();
	while(ch<'0'||ch>'9'){if(ch=='-')f=-f;ch=getchar();}
	while(ch>='0'&&ch<='9'){ret=ret*10+ch-'0';ch=getchar();}
	return ret*f;
}
int ABS(int x){return x<0?-x:x;}
inline bool check(int x)
{
	static int A[15],len;
	len=0;
	while(x){A[++len]=x%10;x/=10;}
	for(int i=1;i<len;i++)
		if(ABS(A[i+1]-A[i])<2)
			return false;
	return true;
}
inline void MakeTable()
{
	freopen("Table.txt","w",stdout);
	register int i,ans=0;
	for(i=1;i<=2000000000;i++)
	{
		if(check(i))
			ans++;
		if(i%1000000==0)
			printf("%d,",ans);
	}
}
inline int Solve(int n)
{
	int ret=table[n/1000000];
	for(int i=n/1000000*1000000+1;i<=n;i++)
		if(check(i))
			ret++;
	return ret;
}
int main()
{
//	MakeTable();
	scanf("%d%d",&A,&B);
	printf("%d\n",Solve(B)-Solve(A-1));
	return 0;
}