按数组升序排序

Question

我可以让我的程序按降序排序，但不能按升序排序。我无法让我的代码在它们之间切换。我不应该只是能够将 -- 切换到 ++ 吗？我需要使用选择排序。在我的冒泡排序代码中，我可以更改一些小东西。这里是这样吗？还是我必须写一个完全不同的部分？

import javax.swing.*;
import java.io.*;
import java.util.*;

public class Gates_sortingSelection{

public static void main(String[] args){

  //ask user for the amount of values in the array      
  String amountS;
  amountS = JOptionPane.showInputDialog(null, "How many numbers would you like to sort?", 
        "Sorting Arrays", JOptionPane.INFORMATION_MESSAGE);
  int amount = Integer.parseInt(amountS);

  JOptionPane.showMessageDialog (null, "Please enter " + amount + " numbers you wish to sort.", 
        "Sorting Arrays", JOptionPane.INFORMATION_MESSAGE);

  int[] numbers = new int [amount];

  //a loop that will ask for as many numbers the user specified
  for(int i = 1; i <= amount; i++){
     String tempS = JOptionPane.showInputDialog("Number " + i + ": ");
     int temp = Integer.parseInt(tempS);
     numbers[i - 1] = temp; 
  }

  String which = JOptionPane.showInputDialog(null, "Would you like your values sorted in ascending (A), or descending (D) order?", 
        "Sorting Arrays", JOptionPane.INFORMATION_MESSAGE);

  if(!(which.equals("A") || which.equals("D"))){
     which = JOptionPane.showInputDialog(null, "Please choose ascending (A) or descending (D).", 
        "Sorting Arrays", JOptionPane.INFORMATION_MESSAGE);
  }

  if(which.equals("D")){
     //initialize the descending method
     sortD(numbers);
  }

  if(which.equals("A")){
     //initialize the ascending method
     sortA(numbers);
  }

}

public static void sortD(int[] tosort){

  int[] original = tosort.clone();      //copy the original array to send into the next method

  int i, j, first, temp;
  for(i = tosort.length-1; i > 0; i--){

     first = 0;     //initializes to subscript of first element
     for(j=1; j<=i; j++){    //locates the smallest elememt between position 1 and i 
        if(tosort[j] < tosort[first])
        first = j;
     }

     temp = tosort[first];   //swaps the smallest number found with the element in position i

     tosort[first] = tosort[i];
     tosort[i] = temp;
  }

print(tosort, original);      //send both the original array and the sorted array to the next method to print

}

这是升序代码开始的地方

public static void sortA(int[] tosort){

  int[] original = tosort.clone();      //copy the original array to send into the next method

  int i, j, first, temp;
  for(i = tosort.length-1; i > 0; i++){

     first = 0;     //initializes to subscript of first element
     for(j=1; j>=i; j++){    //locates the smallest elememt between position 1 and i 
        if(tosort[j] < tosort[first])
        first = j;
     }

     temp = tosort[first];   //swaps the smallest number found with the element in position i

     tosort[first] = tosort[i];
     tosort[i] = temp;
  }

print(tosort, original);      //send both the original array and the sorted array to the next method to print

}


public static void print(int[] sorted, int[] unsorted){

  //print the original array, and the sorted array
  JOptionPane.showMessageDialog (null, "Your original five numbers are: " 
           + Arrays.toString(unsorted) + ". \nYour new five numbers are: " 
           + Arrays.toString(sorted) + ".", "Sorted Arrays", JOptionPane.INFORMATION_MESSAGE);
}


}

Answer 1

如果你只需要排序，你可以使用 Arrays.sort(anArray) 而不是自己实现。

Answer 2

在您的 sortA 方法中，以下行有错误

for(i = tosort.length-1; i > 0; i++){

您不能从最后一个索引开始，然后向上增加您的计数器。试试这个：

for(i = tosort.length-1; i > 0; i--){

此外，for 循环中的内部行应更改为

for (j = 0; j <= i; j++) { // locates the greatest elememt between
                                        // position 0 and i
                if (tosort[j] > tosort[first])
                    first = j;
            } 

既然你想按升序排列，它应该找到最大的数字，而不是最小的。

Answer 3

您的代码中还有其他错误，但我不会尝试反转整个排序算法，只是比较。不要将最小的数字排序到数组的头部，而是瞄准最大的数字。因此，如果 sortAscending 是一个确定排序方向的布尔值，请使用以下代码：

if((tosort[j] < tosort[first] && sortAscending) || (tosort[j] > tosort[first] && !sortAscending) {
    first = j;
}