# poj3181 Dollar Dayz (DP+大数)

Dollar Dayz
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Appoint description:

Description

Farmer John goes to Dollar Days at The Cow Store and discovers an unlimited number of tools on sale. During his first visit, the tools are selling variously for \$1, \$2, and \$3. Farmer John has exactly \$5 to spend. He can buy 5 tools at \$1 each or 1 tool at \$3 and an additional 1 tool at \$2. Of course, there are other combinations for a total of 5 different ways FJ can spend all his money on tools. Here they are:

```        1 @ US\$3 + 1 @ US\$2
1 @ US\$3 + 2 @ US\$1
1 @ US\$2 + 3 @ US\$1
2 @ US\$2 + 1 @ US\$1
5 @ US\$1```
Write a program than will compute the number of ways FJ can spend N dollars (1 <= N <= 1000) at The Cow Store for tools on sale with a cost of \$1..\$K (1 <= K <= 100).

Input

A single line with two space-separated integers: N and K.

Output

A single line with a single integer that is the number of unique ways FJ can spend his money.

Sample Input

5 3

Sample Output

5
1个DP题 不过由于数太大了。。。所以我选用的java...

import java.math.*; import java.util.*; public class Main { public static void main(String[] args) { Scanner sca =new Scanner(System.in); int k,n; while(sca.hasNext()) { n=sca.nextInt(); k=sca.nextInt(); BigInteger dp []=new BigInteger; for(int i=0;i<1005;i++) dp[i]=BigInteger.ZERO; dp=BigInteger.ONE; for(int i=1;i<=k;i++){ for(int j=0;j<=n;j++){ if(j>=i&&dp[j-i]!=BigInteger.ZERO){ dp[j]=dp[j].add(dp[j-i]); } } } System.out.println(dp[n]); } } } ------分隔线----------------------------

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