java链表高级编程题

通过编码实现单链表稍微复杂点的操作功能:

1 查找链表倒数最后的N节点

public Node findNodeLastTopN(Node head,int n ){
    if(head == null||n<1){
        return null;
    }
    Node previous = head;
    Node current = head;
    for(int i = 0;i<n-1;i++){
        if(current == null){
            return null;
        }
        current = current.next;
    }
    while(current.next!=null){
        previous = previous.next;
        current = current.next;
    }
    return previous;
}

2 删除链表中倒数最后的N节点

public Node deleteNodeLastTopN(Node head,int n ){
    if(head == null||n<1){
        return null;
    }
    Node first = head;
    Node second = head;
    for(int i = 0;i<n-1;i++){
        if(second == null){
            return null;
        }
        second = second.next;
    }
    while(second.next!=null){
        first = first.next;
        second = second.next;
    }
    return first;
}

3 判断链表中是否有环

public boolean nodeHasCycle(Node head){
    if(head == null|| head.next == null){
        return false;
    }
    Node slow,fast;
    fast = head.next;
    slow = head;
    while(fast!=slow){
        if(fast==null||fast.next==null){
            return false;
        }
        fast = fast.next.next;
        slow = slow.next;
    }
    return true;
}

4 判断两个链表中是否有交点

public static boolean nodeIsIntersect(Node head1, Node head2) {
    if (head1 == null || head2 == null) {
        return false;
    }
    Node tail1 = head1;
    // 找到链表1的最后一个节点
    while (tail1.next != null) {
        tail1 = tail1.next;
    }
    Node tail2 = head2;
    // 找到链表2的最后一个节点
    while (tail2.next != null) {
        tail2 = tail2.next;
    }

    return tail1 == tail2;
}

5 获取两个相交的链表第一个结点

public static Node getIntersectFirstNode(Node head1, Node head2) {
    if (head1 == null || head2 == null) {
        return null;
    }
    int len1 = 1;
    Node tail1 = head1;
    while (tail1.next != null) {
        tail1 = tail1.next;
        len1++;
    }

    int len2 = 1;
    Node tail2 = head2;
    while (tail2.next != null) {
        tail2 = tail2.next;
        len2++;
    }

    // 不相交直接返回NULL
    if (tail1 != tail2) {
        return null;
    }

    Node n1 = head1;
    Node n2 = head2;

    // 略过较长链表多余的部分
    if (len1 > len2) {
        int k = len1 - len2;
        while (k != 0) {
            n1 = n1.next;
            k--;
        }
    } else {
        int k = len2 - len1;
        while (k != 0) {
            n2 = n2.next;
            k--;
        }
    }

    // 一起向后遍历，直到找到交点
    while (n1 != n2) {
        n1 = n1.next;
        n2 = n2.next;
    }

    return n1;
}

6 删除链表中重复的元素

public Node deleteRepeatNode(Node head){
    if(head == null){
        return null;
    }
    Node node = head;
    while(node.next != null){
        if(node.data == node.next.data){
            node.next = node.next.next;
        }else{
            node = node.next;
        }
    }
    return head;
}