Java选择排序算法

来源：互联网发布：php 上传工具编辑：程序博客网时间：2024/05/21 02:49

O(n^2）级别的排序算法

优点

-基础
-编码简答，易于实现，简单场景的首选
-特殊情况下，简单的排序算法更加有效
-简单的排序算法衍生出复杂的排序算法

选择排序

public class SelectionSort {    public void selectionSort(int[] arr, int n) {        for (int i = 0; i < n; i++) {            // 寻找[i,n)区间里的最小值            int minIndex = i;            for (int j = i + 1; j < n; j++) {                if (a[j].compareTo(a[minIndex]) < 0) {                    minIndex = j;                }                temp = a[i];                a[i] = a[minIndex];                a[minIndex] = temp;            }        }    }    public static void main(String[] args) {        int[] a = {10,9,8,7,6,5,4,3,2,1};        SelectionSort selectionSort = new SelectionSort();        selectionSort.selectionSort(a, a.length);        for (int i : a) {            System.out.print(i);        }    }}

泛型选择排序

-自定义类Student

public class Student implements Comparable<Student> {    private String name;    private Integer score;    public Student(String name, Integer score) {        super();        this.name = name;        this.score = score;    }    public String getName() {        return name;    }    public void setName(String name) {        this.name = name;    }    public Integer getScore() {        return score;    }    public void setScore(int score) {        this.score = score;    }    // Student比较方法，先比较分数再比较名字    @Override    public int compareTo(Student o) {        return this.getScore() != o.getScore() ? this.getScore().compareTo(o.getScore())                : this.getName().compareTo(o.getName());    }    @Override    public String toString() {        return "Student [name=" + name + ", score=" + score + "]";    }}

-排序算法

public class SelectionSort {    // 实现泛型排序    public static  <T extends Comparable<? super T>> void  selectionSort(T[] a, int n) {        for (int i = 0; i < n; i++) {            // 寻找[i,n)区间里的最小值            int minIndex = i;            for (int j = i + 1; j < n; j++) {                if (a[j].compareTo(a[minIndex])<0) {                    minIndex = j;                    T temp;                    temp =  a[i];                    a[i] = a[minIndex];                    a[minIndex] = temp;                }            }        }    }    public static void main(String[] args) {        // 泛型时不能采用基本类型        System.out.println("====整型====");        Integer[] a = {10,9,8,7,6,5,4,3,2,1};        selectionSort(a, a.length);        for (int i : a) {            System.out.print(i);            System.out.print(" ");        }        System.out.println();        System.out.println("====双精度====");        Double[] b = {10.1,9.1,8.1,7.1,6.1,5.1,4.1,3.1,2.1,1.1};        selectionSort(b, b.length);        for (Double j : b) {            System.out.print(j);            System.out.print(" ");        }        System.out.println();        System.out.println("====字符串====");        String[] c = {"D","C","B","A"};        selectionSort(c, c.length);        for (String l : c) {            System.out.print(l);            System.out.print(" ");        }        System.out.println();        System.out.println("====学生====");        Student s1 = new Student("d", 10);        Student s2 = new Student("c", 1);        Student s3 = new Student("b", 1);        Student s4 = new Student("a", 1);        Student[] students = {s1,s2,s3,s4};        selectionSort(students, students.length);        for (Student student : students) {            System.out.println(student);        }    }}

-输出结果

====整型====
1 2 3 4 5 6 7 8 9 10
====双精度====
1.1 2.1 3.1 4.1 5.1 6.1 7.1 8.1 9.1 10.1
====字符串====
A B C D
====学生====
Student [name=a, score=1]
Student [name=b, score=1]
Student [name=c, score=1]
Student [name=d, score=10]

0 0