首页 > 专题系列 > Java解POJ > POJ 2193 Lenny’s Lucky Lotto Lists [解题报告] Java
2013
11-10

POJ 2193 Lenny’s Lucky Lotto Lists [解题报告] Java

Lenny’s Lucky Lotto Lists

问题描述 :

Lenny likes to play the game of lotto. In the lotto game, he picks a list of N unique numbers in the range from 1 to M. If his list matches the list of numbers that are drawn, he wins the big prize.

Lenny has a scheme that he thinks is likely to be lucky. He likes to choose his list so that each number in it is at least twice as large as the one before it. So, for example, if N = 4 and M = 10, then the possible lucky lists Lenny could like are:

1 2 4 8

1 2 4 9

1 2 4 10

1 2 5 10

Thus Lenny has four lists from which to choose.

Your job, given N and M, is to determine from how many lucky lists Lenny can choose.

输入:

There will be multiple cases to consider from input. The first input will be a number C (0 < C <= 50) indicating how many cases with which you will deal. Following this number will be pairs of integers giving values for N and M, in that order. You are guaranteed that 1 <= N <= 10, 1 <= M <= 2000, and N <= M. Each N M pair will occur on a line of its own. N and M will be separated by a single space.

输出:

For each case display a line containing the case number (starting with 1 and increasing sequentially), the input values for N and M, and the number of lucky lists meeting Lenny’s requirements. The desired format is illustrated in the sample shown below.

样例输入:

3
4 10
2 20
2 200

样例输出:

Case 1: n = 4, m = 10, # lists = 4
Case 2: n = 2, m = 20, # lists = 100
Case 3: n = 2, m = 200, # lists = 10000

解题代码:

//* @author: 
import java.util.*;
public class Main
{
 public static void main(String[] args){
   Scanner sc=new Scanner(System.in);
     
   long dp[][]=new long[11][2010];
   int nn=sc.nextInt();
   for (int i=1;i<=2000;i++) dp[1][i]=1;
   for (int i=2;i<=10;i++)
	    for (int j=i;j<=2000;j++)
		for (int k=1;k<=j/2;k++) dp[i][j]+=dp[i-1][k];
    for (int ii=1;ii<=nn;ii++) {
        int n=sc.nextInt();
        int m=sc.nextInt();
	 long ans=0;
	for (int i=n;i<=m;i++) ans+=dp[n][i];
	System.out.printf("Case %d: n = %d, m = %d, # lists = %d\n",ii,n,m,ans);
    }
  }
}

  1. I like your publish. It is great to see you verbalize from the coronary heart and clarity on this essential subject matter can be easily noticed.

  2. “可以发现,树将是满二叉树,”这句话不对吧,构造的树应该是“完全二叉树”,而非“满二叉树”。

  3. 漂亮。佩服。
    P.S. unsigned 应该去掉。换行符是n 不是/n
    还可以稍微优化一下,
    int main() {
    int m,n,ai,aj,bi,bj,ak,bk;
    while (scanf("%d%d",&m,&n)!=EOF) {
    ai = sqrt(m-1);
    bi = sqrt(n-1);
    aj = (m-ai*ai-1)>>1;
    bj = (n-bi*bi-1)>>1;
    ak = ((ai+1)*(ai+1)-m)>>1;
    bk = ((bi+1)*(bi+1)-n)>>1;
    printf("%dn",abs(ai-bi)+abs(aj-bj)+abs(ak-bk));
    }
    }

  4. 一开始就规定不相邻节点颜色相同,可能得不到最优解。我想个类似的算法,也不确定是否总能得到最优解:先着一个点,随机挑一个相邻点,着第二色,继续随机选一个点,但必须至少有一个边和已着点相邻,着上不同色,当然尽量不增加新色,直到完成。我还找不到反例验证他的错误。。希望LZ也帮想想, 有想法欢迎来邮件。谢谢

  5. 其实国内大部分公司对算法都不够重视。特别是中小型公司老板根本都不懂技术,也不懂什么是算法,从而也不要求程序员懂什么算法,做程序从来不考虑性能问题,只要页面能显示出来就是好程序,这是国内的现状,很无奈。

  6. 这道题这里的解法最坏情况似乎应该是指数的。回溯的时候
    O(n) = O(n-1) + O(n-2) + ….
    O(n-1) = O(n-2) + O(n-3)+ …
    O(n) – O(n-1) = O(n-1)
    O(n) = 2O(n-1)

  7. L(X [0 .. M-1],Y [0 .. N-1])= 1 + L(X [0 .. M-2],Y [0 .. N-1])这个地方也也有笔误
    应改为L(X [0 .. M-1],Y [0 .. N-1])= 1 + L(X [0 .. M-2],Y [0 .. N-2])