java - 如何记录整数数组，并打印重复的频率

Question

注意:只是一个练习题，不是为了分数。

这是第一年 Java 类(class)中给出的练习题:

Design and implement an application that reads an arbitrary number of integers, by the user, that are in the range 0 to 50 inclusive, and counts how many occurrences of each are entered. After all the input has been processed, print all of the values (with the number of occurrences) that were entered one or more times. In addition, write a method that returns no value which would compute the average of the occurrences of all numbers entered by the user.

这就是我所拥有的(在我清理它之前，我已经跳过了“平均发生率”部分):

import java.util.Scanner;
public class Main 
{       
public static Scanner scan = new Scanner(System.in);

    public static int[] userIntegers()      // this method will build the array of integers, stopping when an out-of-range input is given
    {
            System.out.println("Enter the number of integers to be recorded:  ");
            int numInts = scan.nextInt();

            int[] userArray = new int[numInts];
            int i = 0;
            while(i < numInts)
            {
                    System.out.println("Enter an integer between 1-50 inclusive:  ");
                    int userInteger = scan.nextInt();
                    if(isValidInteger(userInteger))
                    {
                            userArray[i] = userInteger;
                            i++;
                    }
                    else if(isValidInteger(userInteger) == false)
                    {
                            System.out.println("Try again.");
                    }                       
            }
            return userArray;
    }

    public static void occurrenceOutput(int[] input)         // this method will print the occurrence data for a given array
    {   
        int[] occurrenceArray = new int[51];

            int j = 0;
            while(j < 51)  // iterates through all integers from 0 to 50, while the integer in the array is equal to integer j, the corresponding occurance array element increments.
            {
                    for(int eachInteger : input)
                    {
                            occurrenceArray[j] = (eachInteger == j)? occurrenceArray[j]+=1:  occurrenceArray[j];
                    }
                    j++;
            }               

            int k = 0;
            for(int eachOccurrence : occurrenceArray) // as long as there is more than one occurrence, the information will be printed.
            {
                    if(eachOccurrence > 1)
                    {
                            System.out.println("The integer " + k + " occurrs " + eachOccurrence + " times.");
                    }
                    k++;
            }
    }

    public static boolean isValidInteger(int userInput)     // checks if a user input is between 0-50 inclusive        
    {        
        boolean validInt = (51 >= userInput && userInput >= 0)?  true:  false;
            return validInt;
    }

    public static void main(String[] args)
    {
        occurrenceOutput(userIntegers());
    }
}  

有人可以指出我更优雅的方向吗？

编辑:感谢您的帮助!这就是我现在所处的位置:

import java.util.Scanner;
public class simpleHist
{
    public static void main(String[] args)
{
            getUserInputAndPrint();
            getIntFreqAndPrint(intArray, numberOfInts);
    }

    private static int numberOfInts;
    private static int[] intArray;
    private static int[] intFreqArray = new int[51];

    public static void getUserInputAndPrint() 
    {
            //  The user is prompted to choose the number of integers to enter:
            Scanner input = new Scanner(System.in);
            System.out.println("Enter the number of Integers:  ");
            numberOfInts = input.nextInt();

            //  The array is filled withchInteger = integer; integers ranging from 0-50:
            intArray = new int[numberOfInts];
            int integer = 0;
            int i = 0;
            while(i < intArray.length)
            {
                    System.out.println("Enter integer value(s):  ");
                    integer = input.nextInt();
                    if(integer > 50 || integer < 0)
                    {
                            System.out.println("Invalid input.  Integer(s) must be between 0-50 (inclusive).");
                    }
                    else
                    {
                            intArray[i] = integer;
                            i++;
                    }
            }

            // Here the number of integers, as well as all the integers entered are printed:
            System.out.println("Integers: " + numberOfInts);    
            int j = 0;
            for(int eachInteger : intArray)
            {
                    System.out.println("Index[" + j + "] : " + eachInteger);
                    j++;
            }
    }

public static void getIntFreqAndPrint(int[] intArray, int numberOfInts)
{
    //  Frequency of each integer is assigned to its corresponding index of intFreqArray:
    for(int eachInt : intArray)
    {
        intFreqArray[eachInt]++;
    }

    //  Average frequency is calculated:
    int totalOccurrences = 0;
    for(int eachFreq : intFreqArray)
    {
        totalOccurrences += eachFreq;
    }
    double averageFrequency = totalOccurrences / numberOfInts;

    //  Integers occurring more than once are printed:
    for(int k = 0; k < intFreqArray.length; k++)
    {
        if(intFreqArray[k] > 1)
        {
            System.out.println("Integer " + k + " occurs " + intFreqArray[k] + " times.");
        }
            }

            //  Average occurrence of integers entered is printed:
            System.out.println("The average occurrence for integers entered is " + averageFrequency);
            }
    }

Answer 1

您实际上是在寻找 histogram .您可以使用 Map<Integer,Integer> 来实现它，或者由于元素的范围限制在0-50，可以使用51个元素的数组[0-50]，增加histogram[i]当您阅读时 i .

奖励:理解了这个想法，你就了解了 count-sort 的基础知识