1.爬楼地

爬20个台阶的爬法:=f(19)+f'(18)

经典斐波拉契数列问题 

public class demo4 {
    //爬楼梯问题
    public static void main(String[] args) {
        System.out.println(getSum(20));
    }

    public static int getSum(int n) {
        if (n == 1)
            return 1;
        if (n == 2)
            return 2;
        return getSum(n - 1) + getSum(n - 2);
    }
}

2.按照要求排序问题

package lx;

import java.util.Arrays;
import java.util.Comparator;

public class demo1 {
    public static void main(String[] args) {
        Girlfriend g1 = new Girlfriend("zhangsan", 18, 90);
        Girlfriend g2 = new Girlfriend("lisi", 19, 100);
        Girlfriend g3 = new Girlfriend("wangwu", 20, 110);
        //定义数组存储对象
        Girlfriend[] arr = {g1, g2, g3};
        // Arrays.sort(arr, new Comparator<Girlfriend>() {
           /* public int compare(Girlfriend o1, Girlfriend o2) {
                //按照年龄的大小进行比较,年龄一样,按照身高比较,身高一样按照姓名的字母比较
                double tmp = o1.getAge() - o2.getAge();
                tmp = tmp == 0 ? o1.getHeight() - o2.getHeight() : tmp;
                tmp = tmp == 0 ? o1.getName().compareTo(o2.getName()) : tmp;
                if (tmp < 0) {
                    return -1;
                } else if (tmp > 0) {
                    return 1;
                } else
                    return 0;
            }
        });*/
        //lambda表达式
        //()->{}
        //():对应抽象方法的形参
        //{}:方法体
        Arrays.sort(arr, (o1, o2) -> {
            //按照年龄的大小进行比较,年龄一样,按照身高比较,身高一样按照姓名的字母比较
            double tmp = o1.getAge() - o2.getAge();
            tmp = tmp == 0 ? o1.getHeight() - o2.getHeight() : tmp;
            tmp = tmp == 0 ? o1.getName().compareTo(o2.getName()) : tmp;
            if (tmp < 0) {
                return -1;
            } else if (tmp > 0) {
                return 1;
            } else
                return 0;

        });
        System.out.println(Arrays.toString(arr));
    }
}

女朋友类

package lx;

public class Girlfriend {
    private String name;
    private int age;
    private int height;

    public Girlfriend(String name, int age, int height) {
        this.name = name;
        this.age = age;
        this.height = height;
    }

    public Girlfriend() {
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }

    public int getHeight() {
        return height;
    }

    public void setHeight(int height) {
        this.height = height;
    }

    @Override
    public String toString() {
        return "Girlfriend{" +
                "name='" + name + '\'' +
                ", age=" + age +
                ", height=" + height +
                '}';
    }
}

3.兔子问题(斐波拉契数列)

package lx;

public class demo2 {
    public static void main(String[] args) {

        //斐波那契数列
        int[] arr = new int[12];
        arr[0] = 1;
        arr[1] = 1;
        for (int i = 2; i < arr.length; i++) {
            arr[i] = arr[i - 1] + arr[i - 2];
        }

        System.out.println(arr[11]);
    }
}

4.猴子吃桃问题

package lx;


public class demo3 {
    public static void main(String[] args) {
        //猴子偷桃问题
        /*
        有一堆桃子,猴子第一天吃了其实一半,并且多吃了一个!
        以后每天猴子都吃当前剩下来的一半,然后多吃一个
        第10天的时候(还没有吃),发现就剩下一个桃子,请问最初总共多少个桃子
        day10 1;
        day9=(day10+1)*2 4
        day8=(day9+1)*2  10
        每一天的桃子的数量都是后一天数量+1,*2
         */


        //method01();
        /*
        1.出口
        day==10 剩下一个
        2. 规律
        每一天的桃子的数量都是后一天数量+1,*2

         */

        System.out.println(getCount(1));
    }

    public static int getCount(int day) {
        if (day <= 0 || day >= 11) {
            System.out.println("当前时间错误");
            return -1;
        }
        //出口
        if (day == 10) {
            return 1;
        } else {// 每一天的桃子的数量都是后一天数量+1,*2
            return (getCount(day + 1) + 1) * 2;
        }
    }

    private static void method01() {
        int day = 0;
        int x = 1;
        int y = 0;
        for (day = 9; day >= 1; day--) {
            y = (x + 1) * 2;
            x = y;
        }
        System.out.println(y);
    }
}