【BZOJ】1655: [Usaco2006 Jan] Dollar Dayz 奶牛商店（背包+高精度）

http://www.lydsy.com/JudgeOnline/problem.php?id=1655

背包就没什么好说的了，裸的完全背包。。

但是我一开始交开了ull都wa了T_T。。

精度太大。。。

。。

打高精度吧。。

#include <cstdio>

#include <cstring>

#include <cmath>

#include <string>

#include <iostream>

#include <algorithm>

#include <queue>

using namespace std;

#define rep(i, n) for(int i=0; i<(n); ++i)

#define for1(i,a,n) for(int i=(a);i<=(n);++i)

#define for2(i,a,n) for(int i=(a);i<(n);++i)

#define for3(i,a,n) for(int i=(a);i>=(n);--i)

#define for4(i,a,n) for(int i=(a);i>(n);--i)

#define CC(i,a) memset(i,a,sizeof(i))

#define read(a) a=getint()

#define print(a) printf("%d", a)

#define dbg(x) cout << #x << " = " << x << endl

#define printarr(a, n, m) rep(aaa, n) { rep(bbb, m) cout << a[aaa][bbb]; cout << endl; }

inline const int getint() { int r=0, k=1; char c=getchar(); for(; c<'0'||c>'9'; c=getchar()) if(c=='-') k=-1; for(; c>='0'&&c<='9'; c=getchar()) r=r*10+c-'0'; return k*r; }

inline const int max(const int &a, const int &b) { return a>b?a:b; }

inline const int min(const int &a, const int &b) { return a<b?a:b; }

const int M=1005;

int n, k;

int f[M][M];

void add(int a[], int b[]) {

	int lena=a[0], lenb=b[0], lenc=max(lena, lenb);

	int k=0, i;

	for(i=1; i<=lenc || k; ++i) {

		k=(a[i]+b[i])/10;

		a[i]+=b[i]; a[i]%=10;

		a[i+1]+=k;

	}

	a[0]=i-1;

}

int main() {

	read(n); read(k);

	f[0][1]=f[0][0]=1;

	for1(i, 1, k) {

		for1(j, i, n)

			add(f[j], f[j-i]);

	}

	int t=f[n][0];

	for3(i, t, 1) print(f[n][i]);

	return 0;

}

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

HINT

Source

Silver