BZOJ 1618: [Usaco2008 Nov]Buying Hay 购买干草 (完全背包)

1618: [Usaco2008 Nov]Buying Hay 购买干草

Time Limit: 5 Sec  Memory Limit: 64 MB
Submit: 906  Solved: 456
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Description

    约翰的干草库存已经告罄,他打算为奶牛们采购日(1≤日≤50000)磅干草.
    他知道N(1≤N≤100)个干草公司,现在用1到N给它们编号.第i个公司卖的干草包重量为Pi(1≤Pi≤5000)磅,需要的开销为Ci(l≤Ci≤5000)美元.每个干草公司的货源都十分充足,可以卖出无限多的干草包.    帮助约翰找到最小的开销来满足需要,即采购到至少H磅干草.

Input

    第1行输入N和日,之后N行每行输入一个Pi和Ci.

Output

    最小的开销.

Sample Input

2 15
3 2
5 3

Sample Output

9

FJ can buy three packages from the second supplier for a total cost of 9.

思路:完全背包。。。注意是买至少V,可以超过。我的做法是算了两倍,然后取最小值(V..2V)

hdu 1114 – Piggy-Bank (完全背包)

F – Piggy-Bank

Time Limit:1000MS     Memory Limit:32768KB     64bit IO Format:%I64d & %I64u

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Description

Before ACM can do anything, a budget must be prepared and the necessary financial support obtained. The main income for this action comes from Irreversibly Bound Money (IBM). The idea behind is simple. Whenever some ACM member has any small money, he takes all the coins and throws them into a piggy-bank. You know that this process is irreversible, the coins cannot be removed without breaking the pig. After a sufficiently long time, there should be enough cash in the piggy-bank to pay everything that needs to be paid. 

But there is a big problem with piggy-banks. It is not possible to determine how much money is inside. So we might break the pig into pieces only to find out that there is not enough money. Clearly, we want to avoid this unpleasant situation. The only possibility is to weigh the piggy-bank and try to guess how many coins are inside. Assume that we are able to determine the weight of the pig exactly and that we know the weights of all coins of a given currency. Then there is some minimum amount of money in the piggy-bank that we can guarantee. Your task is to find out this worst case and determine the minimum amount of cash inside the piggy-bank. We need your help. No more prematurely broken pigs! 

 

Input

The input consists of T test cases. The number of them (T) is given on the first line of the input file. Each test case begins with a line containing two integers E and F. They indicate the weight of an empty pig and of the pig filled with coins. Both weights are given in grams. No pig will weigh more than 10 kg, that means 1 <= E <= F <= 10000. On the second line of each test case, there is an integer number N (1 <= N <= 500) that gives the number of various coins used in the given currency. Following this are exactly N lines, each specifying one coin type. These lines contain two integers each, Pand W (1 <= P <= 50000, 1 <= W <=10000). P is the value of the coin in monetary units, W is it's weight in grams. 
 

Output

Print exactly one line of output for each test case. The line must contain the sentence “The minimum amount of money in the piggy-bank is X.” where X is the minimum amount of money that can be achieved using coins with the given total weight. If the weight cannot be reached exactly, print a line “This is impossible.”. 
 

Sample Input

3
10 110
2
1 1
30 50
10 110
2
1 1
50 30
1 6
2
10 3
20 4
 
 
 
 
完全背包。
注意是要放满,但是由于想要的是value的最小值,所以不合法的状态要赋值成inf而不是-1