英文:
Swap misuse absurdity?
问题
以下是在Java中实现的逆向数组代码。我按照逻辑进行了解析，我觉得它应该能够工作。
public static int[] reverseArray(int[] arr){
int temp = 0;
int[] newArr;
newArr = Arrays.copyOf(arr, arr.length);
for (int i = 0; i < arr.length - 1; i++){
temp = newArr[i];
newArr[i] = newArr[arr.length - 1 - i];
newArr[arr.length - 1 - i] = temp;
}
return newArr;
}
我传入了一个数组 [1, 2, 3, 4, 5]。
它返回给我只有第一个和最后一个数字交换的数组。
返回 [5, 2, 3, 4, 1]。
英文:
the following is a reverse array implementation in java. I walked through it logically and I feel like it should work.
public static int[] reverseArray(int[] arr){
int temp = 0;
int[] newArr;
newArr = Arrays.copyOf(arr, arr.length);
for (int i = 0; i < arr.length - 1; i++){
temp = newArr[i];
newArr[i] = newArr[arr.length - 1 - i];
newArr[arr.length - 1 - i] = temp;
}
return newArr;
}
I pass in an array [1, 2, 3, 4, 5]
It returns to me only the first the the last number swapped.
Returns [5, 2, 3, 4, 1]
答案1
得分: 3
你正在循环直到数组的末尾，这导致你的逻辑失败。
你必须循环到 arr.length/2，而不是循环整个数组。循环整个数组会导致你的程序执行以下操作 -
- 交换元素并在循环的前半部分反转数组：现在，当循环达到索引 -
arr.length/2时，所有元素已经彼此交换，你的数组已经被反转。 - 在循环的后半部分重新开始对所有元素进行交换：这实际上开始将数组元素放回到它们原来的位置。当循环达到索引
arr.length - 1时，你的数组会恢复到原来的形式。
解决方法：
当你达到 arr.length/2 时，只需停止循环，你的程序就会正常运行。因此，reverseArray 函数中的 for 循环应如下所示：
for (int i = 0; i < arr.length/2 ; i++)
英文:
You are looping till the end of Array which causes your logic to fail.
You must loop till arr.length/2 instead of looping the whole array. Looping the whole array will cause your program to do the following -
- swap elements and reverse the array in first half of loop : Now when the loop reaches the index -
arr.length/2, all elements have already been swapped with each other and your Array has been reversed. - Reswapping back of all the elements starts in the second half of loop : This effectively starts putting the Array elements back into their original place. When the loop reaches the index
arr.length - 1, your Array is reversed back to the original form it was.
Solution :
Just stop the loop when you reach arr.length/2 and your program will run fine. So your for-loop in reverseArray function should be as follows :
for (int i = 0; i < arr.length/2 ; i++)
答案2
得分: 1
你在两次交换元素。
在你的示例中，当i为1时，你交换了元素1和3。然后当i为3时，你交换了元素3和1，实际上将它们放回了它们最初的位置。
英文:
You are swapping elements twice.
In your example, when i is 1, you swap elements 1 and 3. Then when i is 3, you swap elements 3 and 1, effectively putting them back where they were originally.
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