贪心算法——找纸币问题

package greed;

import java.util.Arrays;

/**
 * 找钱问题
 * User: luoweifu
 * Date: 14-1-14
 * Time: 下午8:08
 */
public class GiveChange {
	public static int gaiveChange(MoneyBox[] moneyBoxes, int target) {
		Arrays.sort(moneyBoxes);
		int count = 0;
		for(int i = moneyBoxes.length-1; i >= 0; i--) {
			int currentCount = Math.min(moneyBoxes[i].getCount(), target/moneyBoxes[i].getValue());
			target -= currentCount*moneyBoxes[i].getValue();
			count += currentCount;
		}
		if(target > 0) {
			count = -1;
		}
		return count;
	}

	public static void main(String args[]) {
		MoneyBox[] moneyBoxes = {
			new MoneyBox(1, 3),
			new MoneyBox(2, 0),
			new MoneyBox(5, 2),
			new MoneyBox(10, 1),
			new MoneyBox(20, 0),
			new MoneyBox(50, 3),
			new MoneyBox(100, 5),
		};
		int result = gaiveChange(moneyBoxes, 620);
		if(result > 0)
			System.out.println(result);
		else
			System.out.println("No");
	}
}

/**
 * 钱盒子
 */
class MoneyBox implements Comparable{
	private int value;
	private int count;

	MoneyBox(int value, int count) {
		this.value = value;
		this.count = count;
	}

	int getValue() {
		return value;
	}

	void setValue(int value) {
		this.value = value;
	}

	int getCount() {
		return count;
	}

	void setCount(int count) {
		this.count = count;
	}

	@Override
	public int compareTo(Object o) {
		MoneyBox moneyBox = (MoneyBox)o;
		if(this.value < moneyBox.getValue())
			return -1;
		else if(this.value == moneyBox.getValue())
			return 0;
		else
			return 1;
	}
}