java - 如何编写算法对数组进行升序排序并测量运行时间？

Question

我正在完成一个项目，但无法到达最终目的地。基本上我必须完成控制台应用程序，在我的代码中，有很多离线注释的行，它们给出了完成它的指令。

我对该项目有以下要求:

1. 对名称以“sortMe…”开头的数组进行排序，并且测量分别对每个数组进行排序的运行时间。种类应该是升序。

2. 在任何选定的数组(已排序或未排序)中查找最小值并进行测量运行时间。

3. 查找任意选定数组中特定数字的出现次数(排序或未排序)并测量运行时间。

4. 打印出所选数组的内容。

5.退出!

主类代码:

    /*
 * To change this template, choose Tools | Templates
 * and open the template in the editor.
 */

package da522b_lab3_2013;

import java.io.BufferedReader;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.Scanner;

/**
 * @author Stranger
 * Kristianstad University
 */

public class Main {


    //declaration
    Scanner myScanner;

    int[] sortMeHundredArr;
    int[] sortMeTenThousandArr;
    int[] sortMeMillionArr;

    int[] unSortedHundredArr;
    int[] unSortedTenThousandArr;
    int[] unSortedMillionArr;
    //You can have a currentArray variable here

    boolean firstTime;
    boolean sorted; //You can use the boolean firstTime instead.

    /** Creates a new instance of Main */
    public Main() {

        //Initialization
        myScanner = new Scanner(System.in);

        sortMeHundredArr = new int[100];
        sortMeTenThousandArr = new int[10000];
        sortMeMillionArr = new int[1000000];

        unSortedHundredArr = new int[100];
        unSortedTenThousandArr = new int[10000];
        unSortedMillionArr = new int[1000000];

        firstTime = true;

        //The method fills the arrays with the numbers form  "milliion.txt""
        fillAllArrays();

        //The arrays are identical before the user sort them, after sorting they are different in the order of contents
    }//End of constructor

    public void myMainMethod(){
        while(true){
            printMenu();
            //Only accepts numbers in range of signed integers. It does not take care of entries other than those numbers.
            switch(myScanner.nextInt()){
                case 1:
                    System.out.println("I'll write the code to sort three arrays which their names started with sortMe...");
                    //Write a separate class and some code here and sort the numbers ascending
                    SortingArray sa=new SortingArray();//I am not sure about it's accuracy
                    // - sortMeHundredArr
                    sa.arraySortingHundred(sortMeHundredArr);//I am not sure if this line is placed in the correct way
                    // - sortMeTenThousandArr
                    sa.arraySortingTenthousand(sortMeTenThousandArr);//I am not sure if this line is placed in the correct way
                    // - sortMeMillionArr
                    sa.arraySortingOneMillion(sortMeMillionArr);//I am not sure if this line is placed in the correct way
                    //Do not forget running time measurement sepaerately for each array
                    firstTime = false;
                    break;

                case 2:
                    //use "boolean sorted" in line 35 to prevent being activated before sorting
                    chooseArrayMenu();

                    System.out.println("I'll write the code to find the minimum in the chosen array ");
                    //write the code of finding minimum, better to implement method(s)/class(es)
                    //The user should have the option to choose any of the sortMe... or unsorted... arrays at a time
                    //Do not forget running time measurement
                    break;

                case 3:
                    //use "boolean sorted" in line 35 to prevent being activated before sorting
                    chooseArrayMenu();

                    System.out.println("I'll write the code to find how many times a specific number is repeated in the chosen array");
                    //Write the code of finding number of occurrences, better to implement method(s)/class(es)
                    //The user should have the option to choose any of the sortMe... or unsorted...  arrays at a time
                    //Do not forget running time measurement
                    break;

                case 4:
                    //use "boolean sorted" in line 36 to prevent being activated before sorting
                    chooseArrayMenu();

                    System.out.println("I'll write the code to print out the content of a chosen array");
                    System.out.println("Array with one million integers may take long time to print out");
                    break;

                case 5:
                    System.out.println("Welcome back");
                    System.exit(0);
                    break;

                default:
                    System.out.println("The input is out of range");
                    break;
            } //End of switch
        } //End of while loop
    } //End of myMainMethod method


    private String printArray(){
        return null; //Null should be changed by you
    } //End of printArray method





    public static void main(String[] args) {
        //One easy way to get rid of static keyword in main method
        Main m1 = new Main();
        m1.myMainMethod();
    }



    private void fillAllArrays(){

        writeToArrayFromFile("million.txt", sortMeHundredArr);
        writeToArrayFromFile("million.txt", sortMeTenThousandArr);
        writeToArrayFromFile("million.txt", sortMeMillionArr);

        writeToArrayFromFile("million.txt", unSortedHundredArr);
        writeToArrayFromFile("million.txt", unSortedTenThousandArr);
        writeToArrayFromFile("million.txt", unSortedMillionArr);
    } //End of fillAllArrays method

    public void writeToArrayFromFile(String fileName, int[] inputArr) {
        int temp = inputArr.length;
        String s;
        try{
            BufferedReader b = new BufferedReader(new InputStreamReader(new FileInputStream(fileName)));
            while (temp>0) {
                s = b.readLine();
                if (s == null) break;
                inputArr[inputArr.length-temp--] = Integer.parseInt(s);
            }//End of try
            b.close();
        } catch (IOException ex) {
            System.out.println(ex.getMessage());
        }  //End of catch
    }//End of writeToArrayFromFile method

    private void chooseArrayMenu(){
        System.out.println("Enter a number between 1 to 6");

        System.out.println("1. Sorted array containing 100 integers");
        System.out.println("2. Sorted array containing 10,000 integers");
        System.out.println("3. Sorted array containing 1,000,000 integers");
        System.out.println("4. Unsorted array containing 100 integers");
        System.out.println("5. Unsorted array containing 10,000 integers");
        System.out.println("6. Unsorted array containing 1,000,000 integers");

    } //End of chooseArrayMenu

    private  void printMenu() {
        if(firstTime){
            System.out.println("\n\n***** Welcome to our application *****");
            System.out.println("******* Please follow the menu *******");
            System.out.println("\n**** Main menu ****");

            System.out.println("Select 1 or 5");
            System.out.println("1. Sort");
            System.out.println("2. (Unavailabe before sorting) Find minimum");
            System.out.println("3. (Unavailabe before sorting) Find number of occurrences");
            System.out.println("4. (Unavailabe before sorting) Print out one array");
            System.out.println("5. Quit");
        } //End of if

        else{
            System.out.println("\n**** Main menu ****");
            System.out.println("select a number between 1 to 5");
            System.out.println("1. Sort");
            System.out.println("2. Find minimum");
            System.out.println("3. Find number of occurrences");
            System.out.println("4. Print out one array");
            System.out.println("5. Quit");

        } //End of else
    } //End of printMenu method


}

ArraySorting 类的代码:

    /*
 * To change this template, choose Tools | Templates
 * and open the template in the editor.
 */
package da522b_lab3_2013;

/**
 *
 * @author Jabir Al Fatah
 */
public class SortingArray {
    public int[] arraySortingHundred(int[] sortMeHundredArr){
    int HundredArrL=sortMeHundredArr.length;
        int temp;
        for(int i=0;i<HundredArrL;i++){
            for(int j=(HundredArrL-1);j>=(i+1);j--){
                if(sortMeHundredArr[j]<sortMeHundredArr[j-1]){
                    temp=sortMeHundredArr[j];
                    sortMeHundredArr[j]=sortMeHundredArr[j-1];
                    sortMeHundredArr[j-1]=temp;

                }
                return sortMeHundredArr;
            }
        }
        return null;
        }
     public int[] arraySortingTenthousand(int[] sortMeTenThousandArr){
         int TenThousandArrL=sortMeTenThousandArr.length;
         int temp;
          for(int i=0;i<TenThousandArrL;i++){
            for(int j=(TenThousandArrL-1);j>=(i+1);j--){
                if(sortMeTenThousandArr[j]<sortMeTenThousandArr[j-1]){
                    temp=sortMeTenThousandArr[j];
                    sortMeTenThousandArr[j]=sortMeTenThousandArr[j-1];
                    sortMeTenThousandArr[j-1]=temp;
     }
    return sortMeTenThousandArr;
}
          }
        return null;

     }
     public int[] arraySortingOneMillion(int[] sortMeMillionArr){
         int millionArrL=sortMeMillionArr.length; 
         int temp;
          for(int i=0;i<millionArrL;i++){
            for(int j=(millionArrL-1);j>=(i+1);j--){
                if(sortMeMillionArr[j]<sortMeMillionArr[j-1]){
                    temp=sortMeMillionArr[j];
                    sortMeMillionArr[j]=sortMeMillionArr[j-1];
                    sortMeMillionArr[j-1]=temp;
     }
    return sortMeMillionArr;
}

     }
   return null;
}
}

如果能得到您的帮助，我将不胜感激。

Answer 1

您必须编写自己的算法来对数组进行排序吗？否则，您可以使用 Arrays.sort()。如果你想测量时间(毫秒):

long startTime = System.currentTimeMillis();
//here your treatment of sorting your array
long endTime = System.currentTimeMillis();
System.out.println(endTime - startTime);