JAVA----代碼練習(3.9)

求斐波那契數列的第n項。(迭代實現)

mport java.util.Scanner;
public class TestDemo {
    public static long fibRec(int num) {
        if(num < 3) {
            return 1;
        }
        return fibRec(num - 1) + fibRec(num - 2);
    }
    public static void main(String[] args) {
        Scanner scan = new Scanner(System.in);
        int num = scan.nextInt();
        if(num <= 0) {
            System.out.println("請輸入一個大於0的正整數!");
        } else {
            long fibRec = fibRec(num);
            System.out.println("斐波那契數列中的第" + num + "項是:" + " " + fibRec);
        }
    }
}

求 N 的階乘

import java.util.Scanner;
public class TestDemo {
    public static int fac(int i) {
        if(i==1) {
            return 1;
        }
        return i*fac(i-1);
    }
    public static void main(String[] args) {
        Scanner scan = new Scanner(System.in);
        int i = scan.nextInt();
        int ret = fac(i);
        System.out.println(ret);
    }
}

求1！+2！+3！+4！+…+n!的和

import java.util.Scanner;
public class TestDemo {
   public static int facAdd(int i) {
       int ret = 1;
       int sum = 0;
        for(int j = 1 ;j <= i ;j++) {
            ret = fac(j);
            sum+=ret;
        }
        return sum;
    }
    public static int fac(int j) {
        if(j==1) {
            return 1;
        }
        return j*fac(j-1);
    }
    public static void main(String[] args) {
        Scanner scan = new Scanner(System.in);
        int i = scan.nextInt();
        int ret = facAdd(i);
        System.out.println(ret);
    }
}

求和的重載

創建方法求兩個數的最大值max2，隨後再寫一個求3個數的最大值的函數max3。

要求：在max3這個函數中，調用max2函數，來實現3個數的最大值計算

public class TestDemo {
    public static int max2(int a,int b) {
        return a >= b ? a : b;
    }
    public static int max3(int a,int b,int c) {
        return max2(max2(a,b),c);
    }
    public static void main(String[] args) {
        int a = 10;
        int b = 20;
        int c = 30;
        int ret2 = max2(a,b);
        int ret3 = max3(a,b,c);
        System.out.println("兩個數中最大值是" + ret2);
        System.out.println("三個數中最大值是" + ret3);
    }
}

在同一個類中定義多個方法：要求不僅可以求兩個整數的最大值，還可以求兩個小數的最大值，以及兩個小數和一個整數的大小關係

import java.util.Scanner;
public class TestDemo {
    public static int max2(int a,int b) {
        return a >= b ? a : b;
    }
    public static double max2(double i,double j ) {
        return i >= j ? i : j;
    }
    public static double max2(int l,double m,double n) {
        return l >= (n >= m ? n : m) ? l: (n >= m ? n : m);
    }
    public static void main(String[] args) {
        /*Scanner scan = new Scanner(System.in);
        int i = scan.nextInt();*/
        int a = 10;
        int b = 20;
        int twoInt = max2(a,b);
        System.out.println("兩個整數中最大值是" + twoInt);

        double i = 35.5;
        double j = 25.6;
        double twoDouble = max2(i,j);
        System.out.println("兩個小數中最大值是" + twoDouble);

        int l = 40;
        double m = 45.5;
        double n = 60.5;
        double intDouble = max2(l,m,n);
        System.out.println("兩個小數和一個整數中最大值是" + intDouble);
    }
}

在同一個類中,分別定義求兩個整數的方法 和 三個小數之和的方法。 並執行代碼，求出結果

public class TestDemo {
    public static int add2(int a,int b) {
        return a+b;
    }
    public static double add2(double i,double j ,double k) {
        return i+j+k;
    }
    public static void main(String[] args) {
        /*Scanner scan = new Scanner(System.in);
        int i = scan.nextInt();*/
        int a = 10;
        int b = 20;
        int addInt = add2(a,b);
        System.out.println("兩個整數的和是" + addInt);

        double i = 35.3;
        double j = 24.2;
        double k = 40.5;
        double addDouble = add2(i,j,k);
        System.out.println("三個小數的和是"+addDouble);
    }
}