URAL1057. Amount of Degrees(DP)

1057

简单的数位DP  刚开始全以2进制来算的 后来发现要找最接近x,y值的那个基于b进制的0,1组合

 #include <iostream>
 #include<cstdio>
 #include<cstring>
 #include<algorithm>
 #include<stdlib.h>
 #include<cmath>
 using namespace std;
 #define LL __int64
 #define INF 1e11
 LL dp[][],pp[][];
 int g1,g2,p[<<];
 void init()
 {
     int i,j;
     for(i =  ; i <=  ; i++)
     {
         pp[i][] = ;
         for(j =  ; j <=  ; j++)
         {
             pp[i][j] = pp[i][j-]*i;
             if(pp[i][j]>INF)
             break;
         }
     }
     dp[][] = ;
     dp[][] = ;
     dp[][] = ;
     for(i = ; i <=  ; i++)
     {
         dp[i][] = ;
         for(j =; j <=  ; j++)
         dp[i][j] = dp[i-][j-]+dp[i-][j];
     }
 }
 void change(int x,int y,int b,int c1[],int c2[])
 {
     int di[],g=,i;
     while(x)
     {
         di[++g] = x%b;
         x/=b;
     }
     for(i = g ; i >= ;i--)
     c1[i] = di[i];
     g1 = g;
     g = ;
     while(y)
     {
         di[++g] = y%b;
         y/=b;
     }
     for(i = g ; i >= ;i--)
     c2[i] = di[i];
     g2 = g;
 }
 LL find(int c[],int k,int len)
 {
     int i,j,o=;
     LL sum=;
     for(i = len ; i >=  ; i--)
     {
         if(c[i]==) continue;
         if(k>=o)
         sum+=dp[i-][k-o];
         o++;
     }
     if(o==k)
     sum++;
     return sum;
 }
 int main()
 {
     int x,y,k,b,j,i;
     int c1[],c2[];
     init();
     scanf("%d%d%d%d",&x,&y,&k,&b);
     if(b!=)
     {
         LL s=,x1=-,x2=-;
         x--;
         for(i =  ; i <= (<<) ; i++)
         {
             s = ;
             for(j =  ; j <=  ; j++)
             if(i&(<<j))
             {
                 s+=pp[b][j];
             }
             if(x1==-&&s>x)
             x1 = i-;
             if(s>y)
             {
                 x2 = i-;
                 break;
             }
         }
         for(j =  ; j >= ; j--)
         if(x1&(<<j))
         {
             c1[j+] = ;
             if(!g1)
             g1 = j+;
         }
         else
         c1[j+] = ;
         for(j =  ; j >= ; j--)
         if(x2&(<<j))
         {
             c2[j+] = ;
             if(!g2)
             g2 = j+;
         }
         else
         c2[j+] = ;
     }
     else
     change(x-,y,b,c1,c2);
     LL s1 = find(c1,k,g1);
     LL s2 = find(c2,k,g2);
     printf("%I64d\n",s2-s1);
     return ;
 }