BZOJ 1655: [Usaco2006 Jan] Dollar Dayz 奶牛商店 (母函数,高精度)

1655: [Usaco2006 Jan] Dollar Dayz 奶牛商店

Time Limit: 5 Sec  Memory Limit: 64 MB
Submit: 353  Solved: 190
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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).

    约翰到奶牛商场里买工具.商场里有K(1≤K≤100).种工具,价格分别为1,2,…,K美元.约翰手里有N(1≤N≤1000)美元,必须花完.那他有多少种购买的组合呢?

Input

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

    仅一行,输入N,K.

Output

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

    不同的购买组合数.

Sample Input

5 3

Sample Output

5
思路:母函数裸题,还卡个高精度。。差评。。。

作者: CrazyKK

ex-ACMer@hust,stackoverflow-engineer@sensetime

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