【BZOJ】【1026】【SCOI2009】Windy数

数位DP

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cxlove基础数位DP第三题

= =预处理是个很有用的东西！然后就是分类讨论！

/**************************************************************
    Problem: 1026
    User: Tunix
    Language: C++
    Result: Accepted
    Time:0 ms
    Memory:1272 kb
****************************************************************/
 
//BZOJ 1026
#include<cmath>
#include<vector>
#include<cstdio>
#include<cstring>
#include<cstdlib>
#include<iostream>
#include<algorithm>
#define rep(i,n) for(int i=0;i<n;++i)
#define F(i,j,n) for(int i=j;i<=n;++i)
#define D(i,j,n) for(int i=j;i>=n;--i)
#define pb push_back
using namespace std;
int getint(){
    int v=0,sign=1; char ch=getchar();
    while(!isdigit(ch)) {if(ch=='-') sign=-1; ch=getchar();}
    while(isdigit(ch))  {v=v*10+ch-'0'; ch=getchar();}
    return v*sign;
}
const int N=1e7+10,INF=~0u>>2;
const double eps=1e-8;
/*******************template********************/
int dp[15][15];
void init(){
    F(i,0,9) dp[1][i]=1;
    F(i,2,10)
        F(j,0,9)
            F(k,0,9)
                if (abs(j-k)>=2) dp[i][j]+=dp[i-1][k];
}
int solve(int n){
    int len=0,bit[15];
    for(;n;n/=10) bit[++len]=n%10;
    bit[len+1]=0;
    int ans=0;
    //长度为1~len-1的
    F(i,1,len-1)
        F(j,1,9)
            ans+=dp[i][j];
    //长度为len，但最高位没达到上界
    F(j,1,bit[len]-1) ans+=dp[len][j];
    //长度为len，且最高位达到上界
    D(i,len-1,1){
        F(j,0,bit[i]-1)
            if (abs(j-bit[i+1])>=2) ans+=dp[i][j];
        if (abs(bit[i]-bit[i+1])<2) break;
    }
    return ans;
}
int main(){
    init();
    int l,r;
    while(scanf("%d%d",&l,&r)!=EOF)
        printf("%d
",solve(r+1)-solve(l));
    return 0;
}