bzoj 1026 [SCOI2009]windy数——数位dp水题

Posted 2020-12-27 narh

题目：https://www.lydsy.com/JudgeOnline/problem.php?id=1026

迷恋上用dfs写数位dp了。

#include<iostream>
#include<cstdio>
#include<cstring>
#include<algorithm>
using namespace std;
const int N=15;
int l,r,dg[N],dp[N][N];
int dfs(int p,int lst,bool fr,bool fx)
{
    if(!p)return 1;
    if(!fx&&dp[p][lst]!=-1)return dp[p][lst];
    int st=(fr?1:0),end=(fx?dg[p]:9);
    int ret=0;
    for(int i=st;i<=end;i++)
        if(fr||(abs(i-lst)>=2))
            ret+=dfs(p-1,i,0,fx&(i==dg[p]));
    if(!fx)dp[p][lst]=ret;
    return ret;
}
int calc(int x)
{
    int cnt=0,ret=0;
    while(x)dg[++cnt]=x%10,x/=10;
    for(int i=1;i<=cnt;i++)
    {
        memset(dp,-1,sizeof dp);//写在这里 
        ret+=dfs(i,0,1,(i==cnt));
    }
    return ret;
}
int main()
{
    scanf("%d%d",&l,&r);
    printf("%d
",calc(r)-calc(l-1));
    return 0;
}