Java中使用数组的选择排序算法

Question

When the program runs, it asks you to enter a product name and price, and then whenever you press -1 it will be stopped and display a list of the entered product and price. However, the problem is I wrote a selection sort algorithm to sort the list by PRICE in ascending order. The output is not what I expected. Have a look at "//Selection Sort" in this code

import java.util.Scanner;

public class ProductPrices {
    private static Scanner keyboard = new Scanner(System.in);
    private static Scanner key = new Scanner(System.in);

    final static int arrayLength = 1000; //maximum array size
    static float[] productPrice = new float[arrayLength]; //stores the prices of products
    static String[] productName = new String[arrayLength]; //stores the names of products

    public static void main(String[] args) {

        System.out.println("SHOPPING. Press -1 to quit anytime.\n");

        for(int i=0; i<arrayLength; i++) {
            System.out.print("Product: ");
            productName[i] = keyboard.nextLine();
            if(productName[i].equals("-1"))
                break;

            System.out.print("Price: $");
            productPrice[i] = key.nextFloat();
            if(productPrice[i] < 0)
                break;
        }

        System.out.println("\nList of the SHOPPING!\n---------------------");
        for(int i=0; i<productPrice.length; i++) {
            if(productName[i] == null || productName[i].equals("-1") || productPrice[i] < 0)
                continue; // null arrays will not be displayed.
            else {
                // Selection sort
                if(productPrice[i] > productPrice[i+1]) {
                    float temp = productPrice[i];
                    productPrice[i] = productPrice[i+1];
                    productPrice[i+1] = temp;
                }
                System.out.printf("Item: %s %.2f\n", productName[i],  productPrice[i]);
            }
        }
    }
}

  For example :::Input::: Product: apple Price: $2.35 Product: pie Price: $1.36 Product: cereal Price: $7.4 Product: -1 :::Output::: Item: apple 1.36 Item: pie 2.35 Item: cereal 0.00 That is incorrect, it should be Item: pie 1.36 Item: apple 2.35 Item: cereal 7.40 

Answer 1

Basically you have implemented selection sort incorrectly. Here is the code to fix it, including a counter to count how many products have been entered (makes the implementation clearer). Also as the other post says, you do not swap the names in your example, only the prices. I think the following should work:

public static void main(String[] args) {
    System.out.println("SHOPPING. Press -1 to quit anytime.\n");
    int prodCount = 0;

    for(int i=0; i<arrayLength; i++) {
        System.out.print("Product: ");
        productName[i] = keyboard.nextLine();
        if(productName[i].equals("-1"))
            break;

        System.out.print("Price: $");
        productPrice[i] = key.nextFloat();
        if(productPrice[i] < 0)
            break;

        prodCount++;
    }

    System.out.println("\nList of the SHOPPING!\n---------------------");
    for (int j = 0; j < prodCount-1; j++) {

       int iMin = j;
       for (int i = j+1; i < prodCount; i++) {
           if (productPrice[i] < productPrice[iMin]) {
               iMin = i;
           }
       }
       if ( iMin != j ) {
           float temp = productPrice[j];
           productPrice[j] = productPrice[iMin];
           productPrice[iMin] = temp;
           String tempn = productName[j];
           productName[j] = productName[iMin];
           productName[iMin] = tempn;
       }
    }
    for(int i=0; i<prodCount; i++) {
        System.out.printf("Item: %s %.2f\n", productName[i],  productPrice[i]);
    }
}