ural1057 Amount of degrees 位数统计

 1 #include <iostream>
 2 #include <string>
 3 using namespace std;
 4 
 5 int f[33][33];
 6 void init(){
 7     f[0][0] =1;
 8     for(int i=1;i<=31;i++){
 9         f[i][0] = f[i-1][0];
10         for(int j=0;j<=i;j++)
11             f[i][j] = f[i-1][j]+f[i-1][j-1];
12     }
13 }
14 
15 int change(int x,int b){
16     string s;
17     while(x){
18         s = (char)(x%b+'0')+s;
19         x = x/b;
20     }
21     for(int i=0;i<s.size();i++)
22         if(s[i]>'1'){
23             for(int j=i;j<s.size();j++)
24                 s[j] = '1';
25             break;
26         }
27     x =0;
28     for(int i=0;i<s.size();i++){
29         x = x|((s[s.size()-1-i]-'0')<<i);
30     }
31     return x;
32 }
33 
34 int cal(int x,int k){
35     int tot =0,ans =0;
36     for(int i=31;i>0;i--){
37         if(x&(1<<i)){
38             tot++;
39             if(tot>k) break;
40             x = x^(1<<i);
41         }
42         if((1<<(i-1))<=x){
43             ans += f[i-1][k-tot];
44         }
45     }
46     if(tot + x==k) ans++;
47     return ans;
48 }
49 
50 int main()
51 {
52     init();
53     int x,y;
54     int k,b;
55     cin>>x>>y>>k>>b;
56     x= change(x,b);
57     y = change(y,b);
58     int resx = cal(x-1,k);
59     int resy = cal(y,k);
60     cout<<resy-resx<<endl;
61     return 0;
62 }