我的 Java 代码有问题...我已经盯着它看了 10 多个小时，但我只是找不到我犯的错误。
我的任务是通过将数组拆分为最大长度为 5 的数组并查找它们的中位数来实现“中位数的中位数”算法。然后你查找这些中位数的中位数并将你的主数组分成两部分，一个具有较小的值，另一个具有较大的值。通过这些数组的长度，您现在可以决定必须在哪个数组中查找哪个位置，然后重复算法，或者如果两个数组的大小相同，则完成。
但不知何故，在大多数情况下，我的算法与正确结果相差一两个位置。所以我认为，某处有一个小错误，可能只是循环的范围或类似的东西。因此，例如，我测试了数组{0,1,2,3,4,5,6,7,8}，因此中位数为 4，但我的程序以3结果作为响应。
我绝对知道，这是一大堆代码，我的问题可能不完全是 StackOverflow 的用途。同样在大多数情况下，我不喜欢让其他人查看我的代码，但我很绝望，因为我无法以某种方式找到我犯的错误。因此，如果你们中的某个人能够从中立的位置查看它，并可能给我一个小提示，为什么它没有按应有的方式工作，我将非常感激。
非常感谢
import java.util.Arrays;
public class MedianSelector {
/**
* Computes and retrieves the lower median of the given array of pairwise
* distinct numbers using the Median algorithm presented in the lecture.
*
* @param numbers array with pairwise distinct numbers.
* @return the lower median.
* @throw IllegalArgumentException if the array is {@code null} or empty.
*/
public static int lowerMedian(int[] numbers) {
// look out for wrong input
if (numbers == null || numbers.length == 0) {
throw new IllegalArgumentException("Input is not correct");
}
if (numbers.length == 1) {
return numbers[0];
}
return getValueAtPosition(numbers, ((numbers.length + 1) / 2) - 1);
}
private static int getValueAtPosition(int[] numbers, int positionI) {
// if the array is smaller then 6 elements
// find median immediately
if (numbers.length <= 5) {
return smallArraySort(numbers);
}
// splitting the array into small arrays of maximum size 5
int fields = 0;
// checking if the array is split-able in only arrays of length 5
// if not, then put the remaining values into an array of size <5
if (numbers.length % 5 == 0) {
fields = numbers.length / 5;
} else {
fields = numbers.length / 5 + 1;
}
// creating an array to hold all the smaller arrays
int[][] splitted = new int[fields][];
// filling the array with the smaller arrays if every smallArray has size 5
if (numbers.length % 5 == 0) {
for (int i = 0; i <= splitted.length - 1; i++) {
int[] smallArray = new int[5];
for (int j = i * 5; j < (i + 1) * 5; j++) {
smallArray[j % 5] = numbers[j];
}
splitted[i] = smallArray;
}
} else {
// filling the array with the smallerArrays if the last array is smaller then 5
for (int i = 0; i < splitted.length - 1; i++) {
int[] smallArray = new int[5];
for (int j = i * 5; j < (i + 1) * 5; j++) {
smallArray[j % 5] = numbers[j];
}
splitted[i] = smallArray;
}
int[] smallArray = new int[numbers.length % 5];
for (int j = 0; j < numbers.length % 5; j++) {
smallArray[j] = numbers[(numbers.length) - (numbers.length % 5) + j];
}
splitted[fields - 1] = smallArray;
}
// calculating the median of every small Arrays and writing them into a bigger
// array
int[] medianCollectorArray = new int[fields];
for (int i = 0; i < splitted.length; i++) {
medianCollectorArray[i] = smallArraySort(splitted[i]);
}
// calculating the median of the array of medians recursively
int x = lowerMedian(medianCollectorArray);
// counting the items that are smaller then the median
int counterK = 0;
for (int i = 0; i < numbers.length; i++) {
if (numbers[i] < x) {
counterK++;
}
}
// if the position of x is the position we are looking for, then we have found
// the median
if (counterK == positionI) {
return x;
// if the position we are looking for is left from x, we need to repeat the
// algorithm in all elements, that are smaller then x and
// find positionI there
} else if (positionI < counterK) {
int[] L1 = new int[counterK];
int index = 0;
for (int i = 0; i <= numbers.length - 1; i++) {
if (numbers[i] < x) {
L1[index] = numbers[i];
index++;
}
}
return getValueAtPosition(L1, positionI);
} else {
// if the position we are looking for is right from x, we need to repeat the
// algorithm in all elements, that are bigger then x
// and find (positionI - counterK +1) there
int[] L2 = new int[numbers.length - (counterK + 1)];
int index = 0;
for (int i = 0; i <= numbers.length - 1; i++) {
if (numbers[i] > x) {
L2[index] = numbers[i];
index++;
}
}
return getValueAtPosition(L2, positionI - (counterK + 1));
}
}
/**
* This method calculates the median of an array with max. 5 elements.
*
* @param array an array with maximum 5 elements
* @return the median of this array
*/
private static int smallArraySort(int[] array) {
if (array == null || array.length > 5 || array.length <= 0) {
throw new IllegalArgumentException("This array shall not be sorted by this method!");
}
// TODO: IMPLEMENT A SORTING ALGORITHM BY MYSELF
// sorting the array an returning its median
Arrays.sort(array);
return array[(array.length - 1) / 2];
}
}