HDU1058 DP

Humble Numbers

Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 65536/32768 K (Java/Others)
Total Submission(s): 24194    Accepted Submission(s): 10596

Problem Description

A
number whose only prime factors are 2,3,5 or 7 is called a humble
number. The sequence 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 12, 14, 15, 16, 18,
20, 21, 24, 25, 27, ... shows the first 20 humble numbers.

Write a program to find and print the nth element in this sequence

 

Input

The
input consists of one or more test cases. Each test case consists of
one integer n with 1 <= n <= 5842. Input is terminated by a value
of zero (0) for n.

 

Output

For
each test case, print one line saying "The nth humble number is
number.". Depending on the value of n, the correct suffix "st", "nd",
"rd", or "th" for the ordinal number nth has to be used like it is shown
in the sample output.

 

Sample Input

1
2
3
4
11
12
13
21
22
23
100
1000
5842
0

 

Sample Output

The 1st humble number is 1.
The 2nd humble number is 2.
The 3rd humble number is 3.
The 4th humble number is 4.
The 11th humble number is 12.
The 12th humble number is 14.
The 13th humble number is 15.
The 21st humble number is 28.
The 22nd humble number is 30.
The 23rd humble number is 32.
The 100th humble number is 450.
The 1000th humble number is 385875.
The 5842nd humble number is 2000000000.

 

Source

University of Ulm Local Contest 1996

题意：

求第n个质因子只有2,3,5,7的数。

代码：

 //从1开始每个humble数依次乘以2，3,5,7，从小到大排列出来，可以简化为f[i]=min(2*f[a],3*f[b],5*f[c],7*f[d]),当然用麻烦的方法也能做。
 //注意1,2,3，21,22,23,111,112,113英文单词后缀st,nd,rd;11,12,13,10011,10012,10013,这样的和其他的后缀为th.
 #include<iostream>
 #include<cstdio>
 using namespace std;
 int n,a,b,c,d;
 long long f[];
 long min(long A,long B,long C,long D)
 {
     long MIN=A;
     if(B<MIN) MIN=B;
     if(C<MIN) MIN=C;
     if(D<MIN) MIN=D;
     if(MIN==A) a++;
     if(MIN==B) b++;
     if(MIN==C) c++;
     if(MIN==D) d++;
     return MIN;
 }
 int main()
 {
     a=b=c=d=;
     f[]=;
     for(int i=;i<=;i++)
     f[i]=min(*f[a],*f[b],*f[c],*f[d]);
     while(scanf("%d",&n)&&n)
     {
         if(n%==&&n%!=)
         printf("The %dst humble number is %lld.\n",n,f[n]);
         else if(n%==&&n%!=)
         printf("The %dnd humble number is %lld.\n",n,f[n]);
         else if(n%==&&n%!=)
         printf("The %drd humble number is %lld.\n",n,f[n]);
         else printf("The %dth humble number is %lld.\n",n,f[n]);
     }
     return ;
 }