查找数组方法的模式（java）[重复]

Question

给定一个数字数组，我必须编写方法来查找平均值、中位数、众数等。我已经解决了其他所有问题，但是模式给了我一个地狱般的时间，不知道为什么。

数组为 22, 26, 45, 46, 49, 55, 57, 63, 63, 65, 66, 67, 67, 68, 68, 69, 70, 71, 72, 73, 75, 76, 76、77、77、78、78、78、79、82、82、83、84、85、87、88、88、89、89、91、92、98、99

它返回 22，而答案应该是 78。

这是我的代码：

public static int mode(int[] array){
    int[] countArray = new int[101];

    //counts each number
    for(int i = 0; i < array.length; i++){
      countArray[array[i]]++;
    }// end for loop

    int mode = array[0], modeIndex = 0;

    //finds which number occurs the most
    System.out.println(Arrays.toString(countArray));
    for(int i = 1; i < array.length; i++){
      if(countArray[i] > mode){

        mode = countArray[i];
        modeIndex = i;
        System.out.println(mode + " " + modeIndex);
      }// end if
    }// end for loop

    return modeIndex;
}// end method mode

Answer 1

你有一个bug，需要修改的两行是：

if(countArray[i] > mode){
    mode = countArray[i];

到：

if(countArray[array[i]] > mode){
    mode = array[i];

Answer 2

你的错误是：int mode = array[0]，应该有 int mode = countArray[0] 在循环中，您应该使用 countArray 的大小，而不是数组。 该代码正常工作（结果为 78）

 public static int mode(int[] array){
    int[] countArray = new int[101];

    //counts each number
    for(int i = 0; i < array.length; i++){
      countArray[array[i]]++;
    }// end for loop

    int mode = countArray[0], modeIndex = 0;

    //finds which number occurs the most
    System.out.println(Arrays.toString(countArray));
    for(int i = 1; i < countArray.length; i++){
      if(countArray[i] > mode){

        mode = countArray[i];
        modeIndex = i;
        System.out.println(mode + " " + modeIndex);
      }// end if
    }// end for loop

    return modeIndex;
}// end method mode`

Answer 3

另一种方法是使用 HashMap

代码：

     int arraya[] = {22, 26, 45, 46, 49, 55, 57, 63, 63, 65, 66, 67, 67, 68, 68, 69, 70, 71, 72, 73, 75, 76, 76, 77, 77, 78, 78, 78, 79, 82, 82, 83, 84, 85, 87, 88, 88, 89, 89, 91, 92, 98, 99};
    List<Integer> array = new ArrayList<>();
    for (int i = 0; i < arraya.length; i++) {
        array.add(arraya[i]);
    }

    HashMap<Integer, Integer> count = new HashMap<>();

    for (Integer i : array) {
        if (count.containsKey(i)) {
            int c = count.get(i);
            count.put(i, c + 1);
        } else {
            count.put(i, 1);
        }
    }

    List listOfOccurance = new ArrayList();
    Set<Map.Entry<Integer, Integer>> entrySet = count.entrySet();
    for (Map.Entry<Integer, Integer> entry : entrySet) {
        System.out.println(entry.getKey() + " = " + entry.getValue());
        listOfOccurance.add(entry.getValue());

    }
    Integer i = (Integer) Collections.max(listOfOccurance);

    while (it.hasNext()) {
        Map.Entry pairs = (Map.Entry) it.next();
        if ((Integer) pairs.getValue() == i) {
            System.out.println(pairs.getKey());
            return;
        }
        it.remove(); // avoids a ConcurrentModificationException
    }

输出：

65 = 1 66 = 1 67 = 2 68 = 2 69 = 1 70 = 1 71 = 1 72 = 1 73 = 1 75 = 1 76 = 2 77 = 2 78 = 3 79 = 1 82 = 2 83 = 1 84 = 1 85 = 1 22 = 1 87 = 1 88 = 2 89 = 2 26 = 1 91 = 1 92 = 1 98 = 1 99 = 1 45 = 1 46 = 1 49 = 1 55 = 1 57 = 1 63 = 2 
The mode is 78