算法－第四版－练习1.2.13解答

用我们对Date的实现作为模板实现Transaction类型。

class Transaction implements Comparable<Transaction>
{
    private final String name;
    private final SmartDate date;
    private final double amount;
    
    public Transaction(String who, SmartDate when, double amount)
    {
        this.name = who;
        this.date = when;
        this.amount = amount;
    }
    
    public Transaction(String transaction)
    {
        String[] s = transaction.split("\\s+");
        if (s.length != 3)
            throw new IllegalArgumentException("Argument illegal " + transaction);
        this.name = s[0];
        this.date = new SmartDate(s[1]);
        this.amount = Double.parseDouble(s[2]);
    }
    
    public String who()
    {
        return this.name;
    }
    
    public SmartDate when()
    {
        return this.date;
    }
    
    public double amount()
    {
        return this.amount;
    }
    
    public String toString()
    {
        return name + " " + date + " " + amount;
    }
    
    public boolean equals(Object that)
    {
        if (this == that) return true;
        if (that == null) return false;
        if (this.getClass() != that.getClass()) return false;
        Transaction t = (Transaction) that;
        if (!this.name.equals(t.name)) return false; 
        if (!this.date.equals(t.date)) return false;
        if (this.amount != t.amount) return false; 
        return true;
    }
    
    public int hashCode()
    {
        int hash = 1;
        hash = hash * 31 + this.name.hashCode();
        hash = hash * 31 + this.date.hashCode();
        hash = hash * 31 + ((Double) this.amount).hashCode();
        return hash;
    }


    @Override
    public int compareTo(Transaction o)
    {
        if (this.amount > o.amount) return 1;
        else if (this.amount < o.amount) return -1;
        else return 0;
    }
}

/**
 * Description : 
 * Author      : mn@furzoom.com
 * Date        : Sep 27, 2016 11:09:47 AM
 * Copyright (c) 2013-2016, http://furzoom.com All Rights Reserved.
 */
package com.furzoom.lab.algs.ch102;

import java.util.Arrays;

/**
 * ClassName    : E10213 <br>
 * Function     : TODO ADD FUNCTION. <br>
 * date         : Sep 27, 2016 11:09:47 AM <br>
 * 
 * @version 
 */
public class E10213
{
    public static void main(String[] args)
    {
        Transaction[] t = new Transaction[4];
        t[0] = new Transaction("Turing 6/17/1990 644.08");
        t[1] = new Transaction("Tarjan 3/26/2002 4121.85");
        t[2] = new Transaction("Knuth 6/14/1999 288.34");
        t[3] = new Transaction("Dijkstra 8/22/2007 2678.40");
        
        System.out.println("Unsorted:");
        for (int i = 0; i < t.length; i++)
        {
            System.out.println(t[i]);
        }
        System.out.println();
        
        System.out.println("Sorted:");
        Arrays.sort(t);
        for (int i = 0; i < t.length; i++)
        {
            System.out.println(t[i]);
        }
        System.out.println();
        
    }

}

完善了SmartDate类：

/**
 * Description : 
 * Author      : mn@furzoom.com
 * Date        : Sep 27, 2016 9:45:00 AM
 * Copyright (c) 2013-2016, http://furzoom.com All Rights Reserved.
 */
package com.furzoom.lab.algs.ch102;


class SmartDate
{
    private final int month;
    private final int day;
    private final int year;
    private static final int[] months = 
        {0, 31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};
    private static final int[] days = 
        {0, 0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334};
    private static final int[] daysLeap =  
        {0, 0, 31, 60, 91, 121, 152, 182, 213, 244, 274, 305, 335};
    private static final String[] weekdays = {"Sunday", "Monday", "Tuesday", "Wednesday", 
            "Thursday", "Friday", "Saturday"};
    
    public SmartDate(int m, int d, int y)
    {
        if (!validate(m, d, y))
            throw new IllegalArgumentException("Argument illegal " + m + "/" + d + "/" + y);
        this.month = m;
        this.day = d;
        this.year = y;
    }
    
    public SmartDate(String date)
    {
        String[] s = date.split("\\/");
        if (s.length != 3)
            throw new IllegalArgumentException("Argument illegal " + date);
        int m = Integer.parseInt(s[0]);
        int d = Integer.parseInt(s[1]);
        int y = Integer.parseInt(s[2]);
        
        if (!validate(m, d, y))
            throw new IllegalArgumentException("Argument illegal " + m + "/" + d + "/" + y);
        
        this.month = m;
        this.day = d;
        this.year = y;
    }
    
    public int month()
    {
        return month;
    }
    
    public int day()
    {
        return day;
    }
    
    public int year()
    {
        return year;
    }
    
    public String dayOfTheWeek()
    {
        // based on 1/1/2000
        int totalDays;
        if (isLeapYear())
        {
            totalDays = daysLeap[month] + day;
        }
        else
        {
            totalDays = days[month] + day;
        }
        
        for (int i = 2000; i < year; i++)
        {
            if (isLeapYear(i))
                totalDays += 366;
            else
                totalDays += 365;
        }
        
        // 1/1/2000 is Saturday
        return weekdays[((totalDays - 1) % 7 + 6) % 7];
    }
    
    public String toString()
    {
        return month + "/" + day + "/" + year;
    }
    
    public boolean equals(Object x)
    {
        if (this == x) return true;
        if (x == null) return false;
        if (this.getClass() != x.getClass()) return false;
        SmartDate that = (SmartDate)x;
        if (this.day != that.day) return false; 
        if (this.month != that.month) return false;
        if (this.year != that.year) return false; 
        return true;
    }
    
    @Override
    public int hashCode()
    {
        int hash = 17;
        hash = hash * 31 + month;
        hash = hash * 31 + day;
        hash = hash * 31 + year;
        return hash;
    }
    
    private boolean validate(int m, int d, int y)
    {
        if (y == 0 || y < -1000 || y > 10000)
            return false;
        
        if (m < 1 || m > 12)
            return false;
        
        if (d < 1 || d > 31)
            return false;
        
        if (d > months[m])
            return false;
        
        if (!isLeapYear() && d > 28)
            return false;
        
        return true;
    }
    
    private boolean isLeapYear(int y)
    {
        if (y % 400 == 0 || (y % 4 == 0 && y % 100 != 0))
        {
            return true;
        }
        else
        {
            return false;
        }
    }
    
    private boolean isLeapYear()
    {
        return isLeapYear(year);
    }
}

算法－第四版－1.2 数据抽象－习题索引汇总

算法－第四版习题索引汇总