Exercise two

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MyInteger类

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import java.util.Scanner;

class MyInteger{
	int value;
	MyInteger(int e){
		this.value = e;
	}
	public int getter() {
		return this.value;
	}
	public boolean isEven() {
		return (this.value % 2 == 0);
	}
	public boolean isOdd() {
		return (this.value % 2 == 1);
	}
	public boolean isPrime() {
		for(int i=2; i*i <= this.value; i++)
		{
			if(this.value % i == 0)
				return false;
		}
		return true;
	}
	public static boolean isEven(int e) {
		return (e % 2 == 0);
	}
	public static boolean isOdd(int e) {
		return (e % 2 == 1);
	}
	public static boolean isPrime(int e) {
		for(int i=2; i*i <= e; i++)
		{
			if(e % i == 0)
				return false;
		}
		return true;
	}
	public static boolean isEven(MyInteger e) {
		return (e.value % 2 == 0);
	}
	public static boolean isOdd(MyInteger e) {
		return (e.value % 2 == 1);
	}
	public static boolean isPrime(MyInteger e) {
		for(int i=2; i*i <= e.value; i++)
		{
			if(e.value % i == 0)
				return false;
		}
		return true;
	}
	public boolean equals(int e) {
		return this.value == e;
	}
	public boolean equals(MyInteger e) {
		return this.value == e.value;
	}
}

public class Main{
	 public static void main(String[] args) {
		 Scanner x = new Scanner(System.in);
		 int a = x.nextInt();
		 int b = x.nextInt();
		 int c = x.nextInt();
		 MyInteger mi = new MyInteger(a);
		 MyInteger ni = new MyInteger(b);
		 System.out.println(mi.isEven());
		 System.out.println(mi.isOdd());
		 System.out.println(mi.isPrime());
		 System.out.println(mi.isPrime(c));
		 System.out.println(mi.isPrime(ni));
		 System.out.println(mi.equals(c));
		 System.out.println(mi.equals(ni));
		 x.close();
	 }
}

Circle2D 类

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import java.util.Scanner;

class Circle2D{
	double x;
	double y;
	double radius;
	
	Circle2D(){
		this.x = 0;
		this.y = 0;
		this.radius = 1;
	}
	
	Circle2D(double xx, double yy, double rr){
		this.x = xx;
		this.y = yy;
		this.radius = rr;
	}
	
	public double getterx() {
		return this.x;
	}
	public double gettery() {
		return this.y;
	}
	public double  getterradius() {
		return this.radius;
	}
	
	public double getArea() {
		return Math.PI * this.radius * this.radius;
	}
	
	public double getPerimeter() {
		return Math.PI * this.radius * 2;
	}
	
	public boolean contains(double xx, double yy) {
		double tmp = (xx - this.x)*(xx - this.x) + (yy - this.y)*(yy - this.y);
		return Math.sqrt(tmp) < this.radius;
	}
	
	public boolean contains(Circle2D e) {
		return Math.abs(this.radius-e.radius) > (Math.sqrt((e.x - this.x)*(e.x - this.x) + (e.y - this.y)*(e.y - this.y)));
	}
	
	public boolean overlaps(Circle2D e) {
		if(this.contains(e)) return false;
		if(e.contains(this)) return false;
		return Math.sqrt((e.x - this.x)*(e.x - this.x) + (e.y - this.y)*(e.y - this.y)) < (Math.abs(this.radius) + Math.abs(e.radius));
	}
}



public class Main1 {
	public static void main(String[] args) {
		Scanner input = new Scanner(System.in);
		Circle2D op1 = new Circle2D(input.nextDouble(),input.nextDouble(),input.nextDouble());
		Circle2D op2 = new Circle2D(input.nextDouble(),input.nextDouble(),input.nextDouble());
		double x = input.nextDouble();
		double y = input.nextDouble();
		System.out.println("The circle's area is "+op1.getArea());
		System.out.println("The circle's perimeter is "+op1.getPerimeter());
		System.out.println("The circle overlaps with the specified circle: "+op1.overlaps(op2));
		System.out.println("The circle contains the specified point: "+op1.contains(x, y));
		System.out.println("The circle contains the specified circle: "+op1.contains(op2));
		input.close();
	}
}

Author与BOok类

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class Author{
	private String name;
	private String email;
	private char gender;
	
	public Author(String name, String email, char gender)
	{
		this.name = name;
		this.email = email;
		this.gender = gender;
	}
	
	public String getName() {
		return this.name;
	}
	
	public String getEmail() {
		return this.email;
	}
	
	public char getgen() {
		return this.gender;
	}
	
	public String toString() {
		String gg;
		if(this.gender == 'm')
			gg = "m";
		else
			gg = "f";
		return "Author[name = " + this.name + ", email = " + this.email + ", gender = " + gg + "]";
	}
}

class Book{
	private String name;
	private Author author;
	private double price;
	private int qty;
	
	Book(String name, Author author, double price, int qty){
		this.name = name;
		this.author = author;
		this.price = price;
		this.qty = qty;
	}
	
	Book(String name, Author author, double price){
		this.name = name;
		this.author = author;
		this.price = price;
		this.qty = 0;
	}
	
	public String getName() {
		return this.name;
	}
	public Author getAuthor() {
		return this.author;
	}
	public double getPrice() {
		return this.price;
	}
	public void setPrice(double e) {
		this.price = e;
	}
	public int getQty() {
		return this.qty;
	}
	public void setQty(int e)
	{
		this.qty = e;
	}
	public String toString() {
		String au = this.author.toString();
		return "Book[name = "+this.getName()+", "+au+", price = "+this.getPrice()+", qty = "+this.getQty() + "]";
	}
}


public class Main2 {
    public static void main(String[] args){
	Author ahTeck = new Author("Tan Ah Teck", "ahteck@nowhere.com", 'm');
	System.out.println(ahTeck);  // Author's toString()

	Book dummyBook = new Book("Java for dummy", ahTeck, 19.95, 99);  // Test Book's Constructor
	System.out.println(dummyBook);  // Test Book's toString()

	// Test Getters and Setters
	dummyBook.setPrice(29.95);
	dummyBook.setQty(28);
	System.out.println("name is: " + dummyBook.getName());
	System.out.println("price is: " + dummyBook.getPrice());
	System.out.println("qty is: " + dummyBook.getQty());
	System.out.println("Author is: " + dummyBook.getAuthor());  // Author's toString()
	System.out.println("Author's name is: " + dummyBook.getAuthor().getName());
	System.out.println("Author's email is: " + dummyBook.getAuthor().getEmail());

	// Use an anonymous instance of Author to construct a Book instance
	Book anotherBook = new Book("more Java", new Author("Paul Tan", "paul@somewhere.com", 'm'), 29.95);
	System.out.println(anotherBook);  // toString()    
    }
}

股票

三种：

  1. 只能买卖一次
  2. 不限买卖次数
  3. 只能买两次
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import java.util.Scanner;

class StockSeller{
	int[] price;
	StockSeller(int[] price){
		this.price = price;
	}
	public int MaxProfit1() {
		if(price.length <= 1) return 0;
		if(price.length == 2) return price[1] > price[0] ? price[1] - price[0] : 0;
		int ret = 0;
		int min = this.price[0];
		for(int i=1; i<price.length; i++)
		{
			if(price[i] > min)
			{
				int cur = price[i] - min;
				ret = ret > cur ? ret : cur;
			}
			else if(price[i] < min)
				min = price[i];
		}
		return ret;
	}
	public int MaxProfit2() {
//		int[] dpbuy = new int[this.price.length];
//		int[] dpsell = new int[this.price.length];
//		
//		dpbuy[0] = -price[0];
//		dpsell[0] = 0;
//		for(int i=1; i<this.price.length; i++)
//		{
//			dpbuy[i] = Math.max(dpbuy[i-1], dpsell[i-1]-price[i]);
//			dpsell[i] = Math.max(dpsell[i-1], dpbuy[i-1] + price[i]);
//		}
//		return dpsell[price.length-1];
		int sum = 0;
	    for(int i=1;i<price.length;i++){
	        if(price[i]-price[i-1] > 0)
	            sum+= price[i]-price[i-1];
	    }
	    return sum;
	}
	
	public int MaxProfit3() {
		if(price.length <= 1) return 0;
		if(price.length == 2) return price[1] > price[0] ? price[1] - price[0] : 0;
		int[] l = new int[price.length];
		int[] r = new int[price.length];
		
		int ret = 0;
		int cur = 0;
		int min = price[0];
		for(int i=0; i<price.length; i++)
		{
			if(price[i] >= min)
			{
				cur = price[i] - min;
				ret = ret > cur ? ret : cur;
			}
			else if(price[i] < min)
				min = price[i];
			l[i] = ret;
		}
		
		ret = 0;
		int max = price[price.length-1];
		for(int i=price.length-1; i>=0; i--)
		{
			if(price[i] <= max)
			{
				cur = max - price[i];
				ret = ret > cur ? ret : cur;
			}
			else if(price[i] > max)
				max = price[i];
			r[i] = ret;
		}
		max = 0;
		for(int i=0; i<price.length-1; i++)
		{
			cur = l[i] + r[i+1];
			if(cur > max) max = cur;
		}
		if(max < r[0])
			max = r[0];
		return max;
	}
}

public class Main3 {
	public static void main(String[] args) {
		Scanner x=new Scanner(System.in);
        while(x.hasNext()){
            int m=x.nextInt();
            int[] price = new int[m];
            for(int i=0;i<m;i++)
                price[i]=x.nextInt();
            StockSeller stock_seller = new StockSeller(price);
            System.out.println(stock_seller.MaxProfit1());
	        System.out.println(stock_seller.MaxProfit2());
	        System.out.println(stock_seller.MaxProfit3());
         }
	x.close();
	}
}
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