Rabbit Breeding and the Greatest Common Divisor (Java Edition)

I. Introduction

Algorithm homework, originally written in C language, but VScode has been convulsed. Recently, the school is studying Java, so you might as well write in a different grammar. My
current feeling: the grammar of JavaSE is actually the same as that of C.

Second, the problem of rabbit reproduction

1. Question
Typical Fibonacci sequence

1 、 1 、2 、 3 、 5 、8 、 13 、 21 、34…

2. Solution
① Method 1

Iteration relation y[ i ] = y[ i-1 ] + y[ i-2 ]

public class Rabit_1 {
    
    
    public static void main(String[] args) {
    
    
        int[] arr=new int[3];
        int i,j;
        System.out.println("请输入当前的月数");
        Scanner scanner=new Scanner(System.in);
        j=scanner.nextInt();
        arr[0]=arr[1]=1;    	//1,2月兔子个数为1
        System.out.println("arr[1] = "+arr[0]);
        System.out.println("arr[2] = "+arr[1]);
        for(i=2;i<j;i++){
    
    
            arr[2]=arr[1]+arr[0];
            System.out.println("arr["+(i+1)+"] = "+arr[2]);
            arr[0]=arr[1];
            arr[1]=arr[2];
        }
    }
}

② Method 2

Iteration relation
a = b+c; b = a+c; c = a+b;

public class Rabit2 {
    
    
    public static void main(String[] args) {
    
    
        int a=1,b=1,c,i;
        for(i=1;i<=4;i++){
    
    
            c=a+b;
            a=b+c;
            b=c+a;        //输出的结果不完美
            System.out.print(a+" "+b+" "+c+" ");
        }
    }
}   

③ Method 3

Iteration relation
a = a+b; b = a+b;

 public class Rabit3 {
    
    
    public static void main(String[] args) {
    
    
        int i,a=1,b=1;
        System.out.print(a+" "+b+" ");
        for(i=1;i<=5;i++){
    
    
            a=a+b;
            b=a+b;
            System.out.print(a+" "+b+" ");
        }
    }
}

3. Find the greatest common divisor

1. Method 1

Exhaustive method

public class Gongyueshu_1 {
    
    
    public static void main(String[] args){
    
    
        int a,b,t;
        System.out.println("输入两个整数");
        Scanner scanner=new Scanner(System.in);
        a=scanner.nextInt();
        b=scanner.nextInt();
        t=a<b? a: b;        //取ab中较小的数
        while(!(a%t==0&&b%t==0)){
    
    
            t--;
        }
        System.out.println(a+"和"+b+"的最大公约数为 "+t);
    }
}

2. Method 2

Roll and divide

 public class Gongyueshu_2 {
    
    
    public static void main(String[] args) {
    
    
        int a,b,r,a1,b1;
        System.out.println("请输入两个整数");
        Scanner scanner=new Scanner(System.in);
        a=scanner.nextInt();
        b=scanner.nextInt();
        a1=a;
        b1=b;
        while(b!=0){
    
    
            r=a%b;
            a=b;
            b=r;
        }
        System.out.println(a1+"和"+b1+"的最大公约数是 "+a);
    }
}

3. Method three

Subtraction

public class Gongyueshu3 {
    
    
    public static void main(String[] args) {
    
    
        Scanner scanner=new Scanner(System.in);
        int a,b;
        System.out.println("请输入两个整数");
        a=scanner.nextInt();
        b=scanner.nextInt();
        if(a==b) {
    
    
            System.out.println("最大公约数是:" + a);
        }else{
    
    
            while(a!=b){
    
    
                if(a>b)
                    a=a-b;
                else
                    b=b-a;
            }
            System.out.println("最大公约数是:" + a);
        }

    }
}

Four, this () usage

1. Introduction
When the teacher mentioned the keyword this in class before, the this. variable name was clearly explained
① Directly refer to
this to point to the current object itself
② Avoid duplication
Formal participation member variables are repeated, use this to distinguish
③ this()
refers to the constructor

this (parameter): Call another form of constructor in this class (should be the first statement in the constructor).

2. Code
① Person class

② Main function Main