标签（空格分隔）： 数位DP
题目链接
记录一下相邻位置的数字,前导零特殊处理
#include<cstdio>
#include<cstring>
#include<iostream>
using namespace std;
typedef long long ll;
ll read()
{
ll x=0,f=1;char ch=getchar();
while(ch<'0'||ch>'9'){if(ch=='-')f=-1;ch=getchar();}
while(ch>='0'&&ch<='9'){x=x*10+ch-'0';ch=getchar();}
return x*f;
}
int k,num[20];
ll l,r,f[20][11][11][11][11][2];
ll dp(int step,int a,int b,int c,int d,int lim)
{
if(step==0)return 1;
if(~f[step][a][b][c][d][lim])return f[step][a][b][c][d][lim];
int x=lim?num[step]:9;
ll res=0;
for(int i=0;i<=x;i++)
{
if(k>=2&&i==d)continue;
if(k>=3&&i==c)continue;
if(k>=4&&i==b)continue;
if(k>=5&&i==a)continue;
res+=dp(step-1,b,c,d,d==10&&i==0?10:i,lim&&i==x);
}
return f[step][a][b][c][d][lim]=res;
}
ll calc(ll x)
{
int len=0;
while(x)num[++len]=x%10,x/=10;
memset(f,-1,sizeof(f));
return dp(len,10,10,10,10,1);
}
int main()
{
while(~scanf("%lld%lld%d",&l,&r,&k))
{
printf("%lld
",calc(r)-calc(l-1));
}
return 0;
}