Java常用算法（冒泡排序、选择排序、二分法、睡眠排序法）

超、凢脫俗 2023-10-10 20:47 19阅读 0赞

冒泡排序  
注意里层循环的：j < arr.length - i - 1，因每次循环都会排好一个数，所以-i可以减少遍历次数

package com.example.demo.test;
    
    import java.util.Arrays;
    
    public class MaoPaoPaiXuDemo {
        
    
        public static void main(String[] args) {
        
            int[] arr = {
        5, 2, 8, 1, 3, 6, 4, 0, 9, 7};
    
            Arrays.stream(maoPao(arr)).forEach(System.out::println);
    
        }
    
        public static int[] maoPao(int[] arr) {
        
            if (arr == null || arr.length <= 1) {
        
                return arr;
            }
    
            int num = 0;
            for (int i = 0; i < arr.length - 1; i++) {
        
                for (int j = 0; j < arr.length - i - 1; j++) {
        
                    if (arr[j] < arr[j + 1]) {
        
                        int t = arr[j];
                        arr[j] = arr[j + 1];
                        arr[j + 1] = t;
                    }
                }
            }
    
            return arr;
        }
    
    }

选择排序

package com.example.demo.test;
    
    import java.util.Arrays;
    
    public class XuanZrPaiXuDemo {
        
    
        public static void main(String[] args) {
        
            int[] arr = {
        5, 2, 8, 1, 3, 6, 4, 0, 9, 7};
    
            Arrays.stream(maoPao(arr)).forEach(System.out::println);
    
        }
    
        public static int[] maoPao(int[] arr) {
        
            if (arr == null || arr.length <= 1) {
        
                return arr;
            }
    
            for (int i = 0; i < arr.length - 1; i++) {
        
                for (int j = i +1; j < arr.length; j++) {
        
                    if (arr[i] < arr[j]) {
        
                        int t = arr[i];
                        arr[i] = arr[j];
                        arr[j] = t;
                    }
                }
            }
    
            return arr;
        }
    }

二分法

package com.example.demo.test;
    
    public class ErFenFaDemo {
        
    
        public static void main(String[] args) {
        
            int[] arr = {
        0, 1, 2, 3, 4, 5, 6, 7, 8, 9};
    
            System.out.println(erFenFa(arr, 5));
    
        }
    
        public static int erFenFa(int[] arr, int searchNum) {
        
            if (arr == null || arr.length == 0) {
        
                return -1;
            }
    
            int l = 0;
            int r = arr.length - 1;
    
            while (l <= r) {
        
                int mid = (l + r) / 2;
                if (searchNum == arr[mid]) {
        
                    return mid;
                } else if (searchNum > arr[mid]) {
        
                    l = mid + 1;
                } else {
        
                    r = mid - 1;
                }
            }
    
            return -1;
        }
    }

最近看到一个有意思的排序法叫睡眠排序法，当然实际肯定不能这么玩

import java.util.concurrent.CountDownLatch;
    
    public class SleepSort {
        
    
        public static void main(String[] args) {
        
            int[] numbers = {
        5, 2, 0, 8, 1, 3, 9, 7, 6, 4};
            sleepSort(numbers);
        }
    
        public static void sleepSort(int[] numbers) {
        
            final CountDownLatch doneSignal = new CountDownLatch(numbers.length);
    
            for (final int num : numbers) {
        
                Thread thread = new Thread(() -> {
        
                    try {
        
                        Thread.sleep(num * 1000);  // Sleep for 'num' seconds
                        System.out.println(num);
                    } catch (InterruptedException e) {
        
                        e.printStackTrace();
                    } finally {
        
                        doneSignal.countDown();
                    }
                });
    
                thread.start();
            }
    
            try {
        
                doneSignal.await();
            } catch (InterruptedException e) {
        
                e.printStackTrace();
            }
        }
    }