【百度面经】HCG 秋招提前批一面

百度HCG 秋招提前批一面面经，难度一般~

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13. 手撕快排

import java.util.*;
import java.io.*;
public class Main{
    public static void main(String[] args) throws IOException{
        BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
        int n = Integer.parseInt(reader.readLine());
        int[] arr = new int[n];
        String[] strs = reader.readLine().split(" ");
        for(int i = 0; i < n; i++){
            arr[i] = Integer.parseInt(strs[i]);
        }
        quickSort(arr, 0, arr.length - 1);
        for(int i = 0; i < arr.length; i++){
            System.out.print(arr[i] + " ");
        }
        reader.close();
    }

    public static void quickSort(int[] arr, int start, int end){
        if(start < end){
            int low = start;
            int high = end;
            int stard = arr[start];
            while(low < high){
                while(low < high && stard <= arr[high]){
                    high--;
                }
                arr[low] = arr[high];
                while(low < high && arr[low] <= stard){
                    low++;
                }
                arr[high] = arr[low];
            }
            arr[low] = stard;
            quickSort(arr, start, low);
            quickSort(arr, low+1 ,end);
        }
    }
}

14. 手撕工厂模式

首先，定义一个形状接口（Shape.java）：

public interface Shape {
    void draw();
}

然后，实现该接口的两个具体类，圆形（Circle.java）和矩形（Rectangle.java）：

// Circle.java
public class Circle implements Shape {
    @Override
    public void draw() {
        System.out.println("Inside Circle::draw() method.");
    }
}

// Rectangle.java
public class Rectangle implements Shape {
    @Override
    public void draw() {
        System.out.println("Inside Rectangle::draw() method.");
    }
}

接下来，创建一个形状工厂（ShapeFactory.java）来生成基于给定信息的形状对象：

public class ShapeFactory {

    // 使用getShape方法获取形状类型的对象
    public Shape getShape(String shapeType) {
        if (shapeType == null) {
            return null;
        }
        if (shapeType.equalsIgnoreCase("CIRCLE")) {
            return new Circle();
        } else if (shapeType.equalsIgnoreCase("RECTANGLE")) {
            return new Rectangle();
        }

        // 默认返回null，可以根据需要抛出异常或返回null
        return null;
    }
}

最后，可以使用这个工厂类来创建形状对象并调用它们的draw方法：

public class FactoryPatternDemo {

    public static void main(String[] args) {
        ShapeFactory shapeFactory = new ShapeFactory();

        // 获取Circle的对象，并调用它的draw方法
        Shape shape1 = shapeFactory.getShape("CIRCLE");
        shape1.draw();

        // 获取Rectangle的对象，并调用它的draw方法
        Shape shape2 = shapeFactory.getShape("RECTANGLE");
        shape2.draw();

        // 获取不存在的形状类型的对象，将返回null
        Shape shape3 = shapeFactory.getShape("SQUARE");
        if (shape3 != null) {
            shape3.draw();
        } else {
            System.out.println("Invalid shape type");
        }
    }
}