java 为了交换这个数组中的数字，我缺少什么？爪哇

What am I missing in order to swap numbers in this array? Java

提问by Admin Lost

So in my assignment, I'm halfway of solving this particular java array (this is an online book; percentage is at 50% in testing phase). However I cannot figure out what I'm missing. For this code, I have to make the input reverse two numbers (of whatever amount is requested). I tried looking online for similar situation but none answered what I needed.

因此，在我的作业中，我正在解决这个特定的 java 数组（这是一本在线书籍；测试阶段的百分比为 50%）。但是我无法弄清楚我错过了什么。对于此代码，我必须使输入反转两个数字（无论请求的数量如何）。我尝试在网上寻找类似的情况，但没有人回答我的需要。

Directions:Write a method swapArrayEnds() that swaps the first and last elements of its array parameter. Ex: sortArray = {10, 20, 30, 40} becomes {40, 20, 30, 10}. The array's size may differ from 4.

说明：编写一个方法 swapArrayEnds() 来交换其数组参数的第一个和最后一个元素。例如：sortArray = {10, 20, 30, 40} 变成 {40, 20, 30, 10}。数组的大小可能不同于 4。

import java.util.Scanner;

public class ModifyArray {
// ANYTHING ABOVE THIS COMMENT CANNOT BE MODIFIED
   public static void swapArrayEnds(int[] sortArray, int numElem) {
      numElem = 4;
      int i = 0;         // Loop index
      int tmpStore = 0;  // Temp variable for swapping

      for (i = 0; i < numElem; ++i) {
         tmpStore = sortArray[i]; // Do swap
         sortArray[i] = sortArray[numElem - 1];
         sortArray[numElem - 1] = tmpStore;
      }

      return;
   }
// ANYTHING BELOW THIS COMMENT CANNOT BE MODIFIED
   public static void main (String [] args) {
      int numElem = 4;
      int[] sortArray = new int[numElem];
      int i = 0;

      sortArray[0] = 10;
      sortArray[1] = 20;
      sortArray[2] = 30;
      sortArray[3] = 40;

      swapArrayEnds(sortArray, numElem);

      for (i = 0; i < numElem; ++i) {
         System.out.print(sortArray[i]);
         System.out.print(" ");
      }
      System.out.println("");

      return;
   }
}

At the moment, my error code is:

目前，我的错误代码是：

Testing with original sortArray = {10, 20, 30, 40}
Expected output:  40 20 30 10 
Your output:  40 10 20 30 
Tests aborted.

I'm not sure how my input became like that, but it merely placed the original last number in front of the original first. How do I have it that the first and last numbers are swapped?

我不确定我的输入是如何变成那样的，但它只是将原始最后一个数字放在原始数字前面。我如何让第一个和最后一个数字交换？

回答by Adrian Colomitchi

Since onlythe ends need to be swapped, and this swap need to happen exactly once(not repeatedly), how about:

由于只需要交换两端，并且这个交换只需要发生一次（不是重复），怎么样：

  // Why do you need yo swap it in a cycle, thus many times???
  /* Commenting faulty code out
  for (i = 0; i < numElem; ++i) {
     tmpStore = sortArray[i]; // Do swap
     sortArray[i] = sortArray[numElem - 1];
     sortArray[numElem - 1] = tmpStore;
  }
  */

  // A single time should do
  tmpStore = sortArray[0]; // Do swap with the starting end
  sortArray[0] = sortArray[numElem - 1];
  sortArray[numElem - 1] = tmpStore;

---

---

(note: I think I'm getting tired of inane comments/answers sending a beginner on fool's errands)

（注意：我想我已经厌倦了向初学者发送傻瓜差事的愚蠢评论/答案）

回答by Lubrious

public static void swapArrayEnds(int sortArray[],int numElem ) {

int t;

t = sortArray[numElem-1];   

//assigning last element to temporary variable

sortArray[numElem-1]=sortArray[0];

//swapping last element with first element

sortArray[0]=t;


}

回答by liducktoe

//a fix the the first answer provided    
import java.util.Scanner;

public class ModifyArray {
// ANYTHING ABOVE THIS COMMENT CANNOT BE MODIFIED
      for (int i = 0; i < numElem; i++) {
         int temp = sortArray[i]; 
         sortArray[i] = sortArray[numElem - 1];
         sortArray[numElem - 1] = temp;
         return;
      }
   }
// ANYTHING BELOW THIS COMMENT CANNOT BE MODIFIED
   public static void main (String [] args) {
      int numElem = 4;
      int[] sortArray = new int[numElem];
      int i = 0;

      sortArray[0] = 10;
      sortArray[1] = 20;
      sortArray[2] = 30;
      sortArray[3] = 40;

      swapArrayEnds(sortArray, numElem);

      for (i = 0; i < numElem; ++i) {
         System.out.print(sortArray[i]);
         System.out.print(" ");
      }
      System.out.println("");

      return;
   }
}

回答by Roadrunner

     public static void swapArrayEnds(int sortArray [],int numElem) {

     int temp = sortArray[0]; 
     sortArray[0] = sortArray[numElem - 1];
     sortArray[numElem - 1] = temp;
  }

回答by mnbv

You may try this approach outlined below.

您可以尝试下面概述的这种方法。

   public static void swapArrayEnds(int[] newArray){

      int num = newArray[0] ;
      newArray[0] = newArray[newArray.length-1];
      newArray[newArray.length-1] = num;
   }