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

  1 #include <iostream>

  2 #include<cstdio>

  3 #include<cstring>

  4 #include<algorithm>

  5 #include<stdlib.h>

  6 #include<cmath>

  7 using namespace std;

  8 #define LL __int64

  9 #define INF 1e11

 10 LL dp[35][25],pp[12][22];

 11 int g1,g2,p[1<<21];

 12 void init()

 13 {

 14     int i,j;

 15     for(i = 3 ; i <= 10 ; i++)

 16     {

 17         pp[i][0] = 1;

 18         for(j = 1 ; j <= 20 ; j++)

 19         {

 20             pp[i][j] = pp[i][j-1]*i;

 21             if(pp[i][j]>INF)

 22             break;

 23         }

 24     }

 25     dp[0][0] = 1;

 26     dp[1][1] = 1;

 27     dp[1][0] = 1;

 28     for(i = 2; i <= 32 ; i++)

 29     {

 30         dp[i][0] = 1;

 31         for(j =1; j <= 20 ; j++)

 32         dp[i][j] = dp[i-1][j-1]+dp[i-1][j];

 33     }

 34 }

 35 void change(int x,int y,int b,int c1[],int c2[])

 36 {

 37     int di[35],g=0,i;

 38     while(x)

 39     {

 40         di[++g] = x%b;

 41         x/=b;

 42     }

 43     for(i = g ; i >= 1;i--)

 44     c1[i] = di[i];

 45     g1 = g;

 46     g = 0;

 47     while(y)

 48     {

 49         di[++g] = y%b;

 50         y/=b;

 51     }

 52     for(i = g ; i >= 1;i--)

 53     c2[i] = di[i];

 54     g2 = g;

 55 }

 56 LL find(int c[],int k,int len)

 57 {

 58     int i,j,o=0;

 59     LL sum=0;

 60     for(i = len ; i >= 1 ; i--)

 61     {

 62         if(c[i]==0) continue;

 63         if(k>=o)

 64         sum+=dp[i-1][k-o];

 65         o++;

 66     }

 67     if(o==k)

 68     sum++;

 69     return sum;

 70 }

 71 int main()

 72 {

 73     int x,y,k,b,j,i;

 74     int c1[35],c2[35];

 75     init();

 76     scanf("%d%d%d%d",&x,&y,&k,&b);

 77     if(b!=2)

 78     {

 79         LL s=0,x1=-1,x2=-1;

 80         x--;

 81         for(i = 0 ; i <= (1<<20) ; i++)

 82         {

 83             s =0 ;

 84             for(j = 0 ; j <= 20 ; j++)

 85             if(i&(1<<j))

 86             {

 87                 s+=pp[b][j];

 88             }

 89             if(x1==-1&&s>x)

 90             x1 = i-1;

 91             if(s>y)

 92             {

 93                 x2 = i-1;

 94                 break;

 95             }

 96         }

 97         for(j = 20 ; j >=0 ; j--)

 98         if(x1&(1<<j))

 99         {

100             c1[j+1] = 1;

101             if(!g1)

102             g1 = j+1;

103         }

104         else

105         c1[j+1] = 0;

106         for(j = 20 ; j >=0 ; j--)

107         if(x2&(1<<j))

108         {

109             c2[j+1] = 1;

110             if(!g2)

111             g2 = j+1;

112         }

113         else

114         c2[j+1] = 0;

115     }

116     else

117     change(x-1,y,b,c1,c2);

118     LL s1 = find(c1,k,g1);

119     LL s2 = find(c2,k,g2);

120     printf("%I64d\n",s2-s1);

121     return 0;

122 }

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