java - 计算链表中给定数字的出现次数

Question

给定一个类 LinkedList

public class LinkedList {

    public Node head = null;

    public class Node {
        public int value;
        public Node next;
    }
}

我想添加一个方法 public int count(int value)计算一个数字在列表中出现的次数。
我尝试了以下操作，但并不总是有效，而且我不确定我做错了什么。

public int count(int value) {

    int counter = 0;

    while(head != null) {

        Node tmp = head.next;

        while(tmp != null) {

            if(head.value == value) {
                counter++;
            }
            tmp = tmp.next;
        }
        head = head.next;
    }
    return counter;
}

此方法适用于 1 4 3 4 4 5 , int value = 4 (它应该返回 3 )
但对于 1 2 3 4 4 5 , int value = 4 ，它返回 1 .

Answer 1

最简单的方法是:遍历列表并为每个包含“值”的节点增加计数。由于您的代码中有几个问题，我试图用注释解释每一行的原因。

public int count(int value) {
    int count = 0;
    
    // 'tmp' is the node we are currently processing.
    // Starting at the head...
    Node tmp = head;
    
    // while we not reached the end of the list
    while(tmp != null) {
        // if the node has the same value we are searching for
        if(tmp.value == value) {
            // increase count since we found the value
            count++;
        }
        // Go to the next node (null if we reached the end of the list).
        tmp = tmp.next;
    }
    
    return count;
}