Amount of Degrees

#include<bits/stdc++.h>
using namespace std;
const int maxn=1e5+5;
int tot,e[40];
long long c[40][40]; 
int l,r,k,b;
template<class t>void red(t &x)
{
    int w=1;
    x=0;
    char ch=getchar();
    while(ch>'9'||ch<'0')
    {
        if(ch=='-')
            w=-1;
        ch=getchar(); 
    }
    while(ch>='0'&&ch<='9')
    {
        x=(x<<3)+(x<<1)+ch-'0';
        ch=getchar();
    } 
    x*=w;
} 
void input()
{
    freopen("input.txt","r",stdin);
}
void dv(int x)
{
    tot=0;
    while(x)
    {
        e[++tot]=x%b;
        x/=b;
    }
    e[++tot]=0;
}
long long dfs(int pos,bool limit,int sum)
{
    if(sum<0)
        return 0;
    if(pos==0)
        return sum?0:1;
    if(!limit&&~c[pos][sum]) 
        return c[pos][sum];
    int ans=0;
    int up=limit?min(e[pos],1):1;
    for(int i=0;i<=up;++i)
        ans+=dfs(pos-1,limit&&(i==e[pos]),sum-i);
    if(!limit)
        c[pos][sum]=ans;
    return ans;
}
long long solve(int x)
{
    if(!x)
        return 0;
    dv(x);
    memset(c,-1,sizeof(c));
    return dfs(tot,1,k);
}
void read()
{
    red(l);
    red(r);
    red(k);
    red(b);    
}
void work()
{
    printf("%lld",solve(r)-solve(l-1));
}
int main()
{
    input();
    read();
    work();
    return 0;
}

定义c[i][j]表示到第i位时还需要j个数字凑齐