Java:将元素从索引重新定位到链表的前面？

Question

我被这个问题困扰了很长一段时间。当我针对重新定位索引 1 的测试运行它时，我从 [A][B][C][D][E] 到 [B][B][C][D][E]。任何帮助将不胜感激。

public void moveToTop(int index) throws IllegalArgumentException {
    if (index > size) {
        throw new IllegalArgumentException();
    }
    if (index == 0) {
        return;
    } else {
        Node ref = first;
        for (int i = 1; i < index; i++) {
            ref = ref.next;
        }
        Node temp = null;
        temp = ref.next;
        ref = temp.next;
        temp = first;
        first = temp;
    }
}

Answer 1

void moveToTop(int index) {
    // index should go until size - 1, not size
    if (index >= size) throw new IllegalArgumentException();
    // index == 0 should return the list unmodified
    if (index == 0) return;

    // We start in the head
    // first = A -> B -> C -> D -> E
    // ref = A -> B -> C -> D -> E
    Node ref = first; 
    for (int i = 0; i < index - 1; i++) {
        // And loop until we find the node before the one we want to move
        // For index = 1, we won't loop, so ref is still equal to first
        ref = ref.next;
    }
    // temp = A.next => temp = B
    Node temp = ref.next;
    // ref (A) is the node before the one we wish to move
    // A.next = B.next => A.next = C => ref = A -> C -> D -> E
    ref.next = temp.next;
    // B.next = A => temp = B -> A -> C -> D -> E
    temp.next = first;
    // first = B -> A -> C -> D -> E
    first = temp;
}