How to rotate a String of space delimited integers in Java?

Suppose I have the following String: "10 30 20 12 34". Now I want to rotate the String but keep the first and last integers fixed. So I should get the 3 outputs should be as follows:

10 20 30 12 34

10 30 12 20 34

10 12 20 30 34

Now, I am trying to first convert the String into an int[] array such that it looks like [10, 30,20, 12, 34] and then create another array, get each element of the original array and insert them in the new array.

This is what I have so far:

String[] arr1 = tree.getPreOrder().split(" ");
int[] arr2 = new int[5];
arr2[0] = Integer.parseInt(arr1[0]);
arr2[1] = Integer.parseInt(arr1[3]);
arr2[2] = Integer.parseInt(arr1[2]);
arr2[3] = Integer.parseInt(arr1[1]);
arr2[4] = Integer.parseInt(arr1[4]);

My issue is, how do I now convert arr2 into the format 10 12 20 30 34. I tried to use join() but it doesn't work.

Also, is there a simpler way to do what I'm trying to do as currently, I am hard coding those values.

Thanks

UPDATE
I created a method which basically rotates the middle values now. However, I got into an issue where one randomly generated String was the same as the original and I would like to avoid that. I'm basically trying to generate only exactly 3 variations of the original string if that helps.
Here's my updated code:

static String randomizeAnswer(String ans) {
String[] arr = ans.split(" ");
int arraySize = arr.length;
String firstElement = arr[0];
String lastElement = arr[arraySize - 1];
String[] arr2 = new String[arraySize - 2];
String arr3[] = new String[arraySize];
arr3[0] = firstElement;
for (int i = 0; i < arraySize - 2; i++) {
arr2[i] = arr[i + 1];
}
Collections.shuffle(Arrays.asList(arr2));
for (int j = 0; j < arr2.length; j++) {
arr3[j + 1] = arr2[j];
}
arr3[arraySize - 1] = lastElement;
return String.join(" ", arr3);
}
for int(i = 0; i<3; i++){
System.out.println(randomizeAnswer("10 30 20 12 34"));
}

UPDATE 2
I eventually managed to make a solution which works but the answer by @WJS below is much better.

static String randomizeAnswer(String ans) {
String[] arr = ans.split(" ");
int arraySize = arr.length;
String firstElement = arr[0];
String lastElement = arr[arraySize - 1];
String[] arr2 = new String[arraySize - 2];
String arr3[] = new String[arraySize];
arr3[0] = firstElement;
for (int i = 0; i < arraySize - 2; i++) {
arr2[i] = arr[i + 1];
}
Collections.shuffle(Arrays.asList(arr2));
for (int j = 0; j < arr2.length; j++) {
arr3[j + 1] = arr2[j];
}
arr3[arraySize - 1] = lastElement;
return String.join(" ", arr3);
}
static String[] generateAnswers(String ans) {
String[] answers = new String[5];
answers[0] = ans;
answers[4] = "None of the answers are correct";
for (int x = 0; x < 3; x++) {
while (true) {
String randomAns = randomizeAnswer(ans);
if (Arrays.stream(answers).anyMatch(randomAns::equals)) {
continue;
} else {
answers[x+1] = randomAns;
break;
}
}
}
return answers;
}

Convert the array to ints. Note that the string values could be rotated without parsing to an int.

String str = "10 30 20 12 34";
int[] vals = Arrays.stream(str.split("\\s+"))
.mapToInt(Integer::parseInt).toArray();

The range to rotate

int start = 1;
int end = 4; // exclusive

An array to save the rotated array of values.

String[] results = new String[end - start];

And now rotating them, converting to a string and storing. Note that the previously rotated array needs to be fed back into the method. But that array is not changed because it is copied in the rotate method.

for (int i = 0; i < end - start; i++) {
vals = rotate(vals, start, end);
// convert to String - can't use join since these are not strings.
// this just streams the results, converts to a string, and joins them into
// a single string.
results[i] =
Arrays.stream(vals).mapToObj(v -> Integer.toString(v))
.collect(Collectors.joining(" "));
}
for (String rotated : results) {
System.out.println(rotated);
}

prints

10 20 12 30 34
10 12 30 20 34
10 30 20 12 34

This simply rotates the array one cell to the left within the specified range. It first makes a copy of the original array. Note the end is exclusive.

public static int[] rotate(int[] arr, int start, int end) {
arr = Arrays.copyOf(arr, arr.length);
int v = arr[start];
for (int i = start; i < end-1; i++) {
arr[i] = arr[i+1];
}
arr[end-1] = v;
return arr;
}
</details>
# 答案2
**得分**: 1
这里是使用Java Streams的我的个人见解。
```java
private static int[] rotate(int[] array, int count) {
if (array.length >= 0 && array.length <= 2) {
return array;
}
return IntStream.range(0, array.length)
.map(i -> (i == 0 || i == array.length - 1) ? i : (i - 1 + count) % (array.length - 2) + 1)
.map(i -> array[i])
.toArray();
}

这会将给定的数组向右旋转* count 个位置，但保持第一个和最后一个索引不变。例如，当 count = 1 *时，数组[10, 30, 20, 12, 34]变为[10, 12, 30, 20, 34]。

如果您想要生成* n *个随机序列，您可以使用下面的代码片段。这将生成与原始数组不相等的数组。

int array = { ... };
int n = 2;
ThreadLocalRandom.current().ints(n, 1, array.length - 2)
    .mapToObj(randomInt -> rotate(array, randomInt))
    .forEach(result -> System.out.println(Arrays.toString(result)));
    // 或者，如果您想将其转换回字符串：
    //.collect(Collectors.mapping(String::valueOf, Collectors.joining(" ")));

Collections::shuffle

当然，您还可以使用Collections::shuffle和List::subList来简单地对除第一个和最后一个元素以外的元素进行洗牌。这个方法是通用的，所以实际上元素是否是整数并不重要。例如，使用Arrays.asList("10 30 20 12 34".split(" "))会产生一个List<String>。

public static <T> List<T> shuffleMid(List<T> list) {
    List<T> newList = new ArrayList<>(list);
    do {
        Collections.shuffle(newList.subList(1, newList.size() - 1));
    } while (newList.equals(list)); // 确保它与原始列表不相等
    return newList;
}

do-while循环确保洗牌后的列表不等于原始列表。这可能是一个天真的实现。

private static int[] rotate(int[] array, int count) {
    if (array.length >= 0 && array.length <= 2) {
        return array;
    }

    return IntStream.range(0, array.length)
        .map(i -> (i == 0 || i == array.length - 1) ? i : (i - 1 + count) % (array.length - 2) + 1)
        .map(i -> array[i])
        .toArray();
}

int array = { … };
int n = 2;
ThreadLocalRandom.current().ints(n, 1, array.length - 2)
    .mapToObj(randomInt -> rotate(array, randomInt))
    .forEach(result -> System.out.println(Arrays.toString(result)));
    // Or, if you want to convert it back to a String:
    //.collect(Collectors.mapping(String::valueOf, Collectors.joining(" ")));

public static <T> List<T> shuffleMid(List<T> list) {
    List<T> newList = new ArrayList<>(list);
    do {
        Collections.shuffle(newList.subList(1, newList.size() - 1));
    } while (newList.equals(list)); // Make sure it is unequal to the original
    return newList;
}

答案3

得分: 1

以下是翻译好的部分：

另一个示例：

      public static void main(String[] args) {
        String treePreOrder = "10 30 20 12 34";    
        String rot1 = rotateMiddle(treePreOrder);
        String rot2 = rotateMiddle(rot1);
    
        System.out.println(treePreOrder);
        System.out.println(rot1);
        System.out.println(rot2);
      }
    
      public static String rotateMiddle(String values) {
        String[] arr = values.split(" ");
        if (arr.length >= 4) {
          String temp = arr[1];
          for(int i=1; i<=(arr.length-3); i++) {
            arr[i] = arr[i+1];
          }
          arr[arr.length-2] = temp;
        }
        return String.join(" ", arr);
      }

输出：

    10 30 20 12 34
    10 20 12 30 34
    10 12 30 20 34

请注意，代码部分已经被保留，没有翻译。

  public static void main(String[] args) {
String treePreOrder = "10 30 20 12 34";    
String rot1 = rotateMiddle(treePreOrder);
String rot2 = rotateMiddle(rot1);
System.out.println(treePreOrder);
System.out.println(rot1);
System.out.println(rot2);
}
public static String rotateMiddle(String values) {
String[] arr = values.split(" ");
if (arr.length >= 4) {
String temp = arr[1];
for(int i=1; i<=(arr.length-3); i++) {
arr[i] = arr[i+1];
}
arr[arr.length-2] = temp;
}
return String.join(" ", arr);
}

10 30 20 12 34
10 20 12 30 34
10 12 30 20 34

答案4

得分: 0

以下是翻译好的内容：

使用另一个辅助数组：

String in = "10 30 20 12 34";
String[] arr_in = in.split(" ");
String[] arr_out = new String[arr_in.length];

arr_out[0] = arr_in[0];
arr_out[arr_out.length-1] = arr_in[arr_in.length-1];

for(int i=arr_in.length-2, j=1; i>0; i--,j++) {
    arr_out[j] = arr_in[i];
}

// 打印输出:
for(int i=0; i<arr_out.length; i++) {
    System.out.println(arr_out[i]);
}

原地旋转：

public static void main(String[] args) {

    String in = "10 30 20 12 34";
    String[] arr = in.split(" ");

    String tmp;
    for(int i=arr.length-2, j=1; i>(arr.length/2); i--,j++) {
        tmp = arr[i];
        arr[i] = arr[j];
        arr[j] = tmp;
    }

    // 打印输出:
    for(int i=0; i<arr.length; i++) {
        System.out.println(arr[i]);
    }
}

        String in = "10 30 20 12 34";
String[] arr_in = in.split(" ");
String[] arr_out = new String[arr_in.length];
arr_out[0] = arr_in[0];
arr_out[arr_out.length-1] = arr_in[arr_in.length-1];
for(int i=arr_in.length-2, j=1;  i>0;  i--,j++)
{
arr_out[j] = arr_in[i];
}
// print:
for(int i=0; i<arr_out.length;i++)
{
System.out.println(arr_out[i]);
}

    
public static void main(String[] args) {
String in = "10 30 20 12 34";
String[] arr = in.split(" ");
String tmp;
for(int i=arr_in.length-2, j=1;  i>(arr_in.length/2);   i--,j++)
{
tmp = arr[i];
arr[i] = arr[j];
arr[j] = tmp;
}
// print:
for(int i=0; i<arr.length;i++)
{
System.out.println(arr[i]);
}
}

答案5

得分: 0

	String[] array = new String[5];
	for(int i = 0; i < 5; i++)
	    array[i] = i + 1 + "";
	 //array[0] = 1, array[1] = 2, array[3] = 3, array[4] = 4, array[5] = 5

	int first = 0;
	int last = array.length - 1;
	
	for(int i = 1; i < array.length / 2; i++){
	    first = i;
	    last = array.length - i - 1;
	    String aux = array[first];
	    array[first] = array[last];
	    array[last] = aux;
	    first++;
	    last--;
	}
	
	for(int i = 0; i < array.length; i++)
	    System.out.print(array[i] + " ");

输出将会是：1 4 3 2 5

	String[] array = new String[5];
for(int i = 0; i < 5; i++)
array[i] = i + 1 + "";
//array[0] = 1, array[1] = 2, array[3] = 3, array[4] = 4, array[5] = 5
int first = 0;
int last = array.length - 1;
for(int i = 1; i < array.length / 2; i++){
first = i;
last = array.length - i - 1;
String aux = array[first];
array[first] = array[last];
array[last] = aux;
first++;
last--;
}
for(int i = 0; i < array.length; i++)
System.out.print(array[i] + " ");

答案6

得分: 0

这绝对有一种更好的方法来利用JDK中的其他API... 但以下是我想出来的方法。

// 根据 [direction] 左/右移 [direction] 个位置。到目前为止，不会抛出 IndexOutOfBoundsException 异常 :)
private static int[] shift(int[] values, int direction) {

    int[] result = new int[values.length];
    for (int i = 0; i < result.length; i++) {
        result[i] = values[(values.length + (i + direction % values.length)) % values.length];
    }
    return result;
}

public static void main(String[] args) {
    int[] values = new int[]{101, 1, 2, 3, 100};
    int[] middleValues = Arrays.copyOfRange(values, 1, values.length-1);
    
    int[][] allCombos = new int[middleValues.length][values.length];
    
    int shiftPtr = 0;
    for (int[] row : allCombos) {
        row[0] = values[0];
        row[row.length-1] = values[values.length-1];
        int[] shifted = shift(middleValues, shiftPtr);
        for (int i = 0; i < middleValues.length; i++) {
            row[i + 1] = shifted[i];                
        }
        shiftPtr++;
        // 并打印测试结果...
        System.out.println(Arrays.toString(row));
    }                                                
}

然后你会得到以下输出：

> [101, 1, 2, 3, 100]
> [101, 2, 3, 1, 100]
> [101, 3, 1, 2, 100]

// shifts by [direction] spaces (-ve and +ve) for left/right. So far so good with not throwing IndexOutOfBoundsExceptions :)
private static int[] shift(int[] values, int direction) {
int[] result = new int[values.length];
for (int i = 0; i < result.length; i++) {
result[i] = values[(values.length + (i + direction % values.length)) % values.length];
}
return result;
}
public static void main(String[] args) {
int[] values = new int[]{101, 1, 2, 3, 100};
int[] middleValues = Arrays.copyOfRange(values, 1, values.length-1);
int[][] allCombos = new int[middleValues.length][values.length];
int shiftPtr = 0;
for (int[] row : allCombos) {
row[0] = values[0];
row[row.length-1] = values[values.length-1];
int[] shifted = shift(middleValues, shiftPtr);
for (int i = 0; i < middleValues.length; i++) {
row[i + 1] = shifted[i];                
}
shiftPtr++;
// and print out to test...
System.out.println(Arrays.toString(row));
}                                                
}

> [101, 1, 2, 3, 100]  
> [101, 2, 3, 1, 100]
> [101, 3, 1, 2, 100]