Java 具有多个键匹配的数组线性搜索

Question

正在尝试执行执行以下操作的程序：

-可以通过用户输入重新运行的程序（while循环）

-允许用户输入所需的数组大小，创建该大小的数组，使用 for 循环将元素输入到数组中，并输入所需的键从中进行线性搜索方法

我想将线性搜索方法修改为return，作为一个数组，arrayName[的所有实例的索引值i] == 键值;这是我被卡住的部分。

例如，如果作为用户我输入 4 作为数组大小； 1、2、2、3为元素； 2 作为线性搜索所需的键，然后它将打印数组 {1, 2} 作为键与元素值匹配的索引。

到目前为止，这是我的代码：

import java.util.Scanner; //Imports Scanner from java.util package

public class LinearSearch2 {
  public static void main (String[] args) {

    //Creates Scanner object for user to input string whether to run program
    Scanner input1 = new Scanner(System.in);
    System.out.print("Run linear search on an array? ");
    System.out.print("(Y = Yes; Type any other character to exit program): ");
    String s = input1.next();
    char runProgram = s.charAt(0);

    /*While loop (this allows for re-running the program with a different 
    set of inputs in the same run depending on the string Scanner object 
    input...see while loop-continuation condition below)*/ 
    while (runProgram == 'y' || runProgram == 'Y') {
      //Creates another Scanner object for entering the array size as integer
      Scanner input2 = new Scanner(System.in);

      //Scans in user input of array size
      System.out.print("Enter desired array size: ");
      int arraySize = input2.nextInt();

      //Creates array based on size input
      double [] numberArray = new double[arraySize];

      //Creates another Scanner object for entering the array numbers as doubles
      Scanner input3 = new Scanner(System.in);

      //Loop to read in input numbers into created array
      for (int i = 0; i < numberArray.length; i++) {
        System.out.print("Enter a number: ");
        numberArray[i] = input3.nextDouble();
      }

      //Creates another Scanner object for entering the key as a doubles
      Scanner input4 = new Scanner(System.in);

      //Scans in user desired key 
      System.out.print("Enter desired key: ");
      double arrayKey = input4.nextDouble();

      //Invokes linear search method
      int [] keyIndices = linearSearch(numberArray,arrayKey);

      //Prints keyIndices array
      for (int i = 0; i < keyIndices.length; i++) {
        System.out.print(keyIndices[i] + " ");
      }

      //Requests if user would like to re-run the program
      System.out.println("Do another linear search on an array? ");
      System.out.print("(Y = Yes; Type any other character to exit program): ");
      //Takes new result of string scanner object to determine if to run the program again or exit
      String s2 = input1.next();
      runProgram = s2.charAt(0);
    }
  }

  //Revised linear search method
  public static int [] linearSearch(double[] list, double key) {
    int [] resultKeyIndices = new int[];
    for (int i = 0; i < list.length; i++) {
      if (key == list[i]){
        return i;
      }
    }
    return -1;
  }
}

Answer 1

问题是分配一个大小合适的数组（匹配数）。此解决方案使用大型数组并在最后调整其大小：

  public static int [] linearSearch(double[] list, double key) {
    int[] indices = int[list.length];
    int n = 0;
    for (int i = 0; i < list.length; i++) {
      if (key == list[i]){
        îndices[n++] = i;
      }
    }
    int[] result = new int[n];
    for (int i = 0; i < n; ++i) {
        result[i] = indices[i];
    }
    return result;
  }

Java 具有多个键匹配的数组线性搜索

Java Linear Search of Array with Multiple Key Matches

java

arrays

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