Mixing+Milk

USACO 1.3 - Mixing Milk
Since milk packaging is such a low margin business, it is important to keep the price of the raw product (milk) as low as possible. Help Merry Milk Makers get the milk they need in the cheapest possible manner.

The Merry Milk Makers company has several farmers from which they may buy milk, and each one has a (potentially) different price at which they sell to the milk packing plant. Moreover, as a cow can only produce so much milk a day, the farmers only have so much milk to sell per day. Each day, Merry Milk Makers can purchase an integral amount of milk from each farmer, less than or equal to the farmer's limit.

Given the Merry Milk Makers' daily requirement of milk, along with the cost per gallon and amount of available milk for each farmer, calculate the minimum amount of money that it takes to fulfill the Merry Milk Makers' requirements.

Note: The total milk produced per day by the farmers will be sufficient to meet the demands of the Merry Milk Makers.

PROGRAM NAME: milk

INPUT FORMAT

Line 1: Two integers, N and M.

The first value, N, (0 <= N <= 2,000,000) is the amount of milk that Merry Milk Makers' want per day. The second, M, (0 <= M <= 5,000) is the number of farmers that they may buy from.

Lines 2 through M+1: The next M lines each contain two integers, Pi and Ai.

Pi (0 <= Pi <= 1,000) is price in cents that farmer i charges.

Ai (0 <= Ai <= 2,000,000) is the amount of milk that farmer i can sell to Merry Milk Makers per day.

SAMPLE INPUT (file milk.in)

100 5

5 20

9 40

3 10

8 80

6 30

OUTPUT FORMAT

A single line with a single integer that is the minimum price that Merry Milk Makers can get their milk at for one day.

SAMPLE OUTPUT (file milk.out)

630

Source Code code format="java" /* ID: wjh3331 LANG: JAVA TASK: milk

import java.io.*; import java.util.Arrays; import java.util.StringTokenizer;

public class milk { public static void main(String[] args) throws IOException { BufferedReader in = new BufferedReader(new FileReader("milk.in")); PrintWriter out = new PrintWriter(new FileWriter("milk.out"));

StringTokenizer st = new StringTokenizer(in.readLine);

int n = Integer.parseInt(st.nextToken); // 사야할 우유 양 int m = Integer.parseInt(st.nextToken); // 농부의 수

// 입력이 0이 들어오면 0을 출력하고 프로그램 종료 if(n == 0 || m == 0) { out.println(0);

out.close; System.exit(0); }

Farmer[] farmers = new Farmer[m];  // 농부 배열

// 농부들 초기화 for(int i = 0 ; i < m; i++) { st = new StringTokenizer(in.readLine);

int p = Integer.parseInt(st.nextToken); int a = Integer.parseInt(st.nextToken);

farmers[i] = new Farmer(p, a); }

// 가격을 기준으로 오름차순으로 정렬 Arrays.sort(farmers);

int sum = 0; int i = 0; while(true) { // 더이상 팔 농부가 없으면 탈출 if(i >= m) { break; }

// 탐욕적 방법으로 계산 if(n >= farmers[i].getAmount) { n -= farmers[i].getAmount; sum += farmers[i].getPrice * farmers[i].getAmount; i++; } else { sum += farmers[i].getPrice * n;       break; }   }

// 결과 출력 out.println(sum);

out.close; System.exit(0); } }

class Farmer implements Comparable { private int price; private int amount;

public Farmer(int price, int amount) { this.price = price; this.amount = amount; }

public int getPrice { return price; }

public int getAmount { return amount; }

public int compareTo(Farmer o) { return this.price - o.price; } } code

Comment 저도 정렬을 이용해서 했습니다. 베스트를 보니... 후덜... 배열에 쏙쏙 집어넣는 방법이 있군요...;;