707. Design Linked List

707_design_linked_list.go

type MyLinkedList struct {
    head *Node
}

type Node struct {
    next *Node
    val int
}


/** Initialize your data structure here. */
func Constructor() MyLinkedList {
    return MyLinkedList{
        head: nil,
    }
}


/** Get the value of the index-th node in the linked list. If the index is invalid, return -1. */
func (this *MyLinkedList) Get(index int) int {
    node := this.head
    
    for i := 0; i < index; i++ {
        if node == nil {
            return -1
        }
        
        node = node.next
    }
    
    if node == nil {
        return -1
    }

    return node.val
}


/** Add a node of value val before the first element of the linked list. After the insertion, the new node will be the first node of the linked list. */
func (this *MyLinkedList) AddAtHead(val int)  {
    this.head = &Node{
        next: this.head,
        val: val,
    }
}


/** Append a node of value val to the last element of the linked list. */
func (this *MyLinkedList) AddAtTail(val int)  {
    if this.head == nil {
        this.head = &Node{
            next: nil,
            val: val,
        }
        
        return
    }
    
    node := this.head
    
    for {
        if node.next == nil {
            node.next = &Node{
                next: nil,
                val: val,
            }
            return
        }

        node = node.next
    }
}


/** Add a node of value val before the index-th node in the linked list. If index equals to the length of linked list, the node will be appended to the end of linked list. If index is greater than the length, the node will not be inserted. */
func (this *MyLinkedList) AddAtIndex(index int, val int)  {
    if this.head == nil {
        if index == 0 {
            this.head = &Node{
                next: nil,
                val: val,
            }
            return
        }
        return
    }
    
    node := this.head
    var i int

    // Iterate to (index - 1) node, if possible
    for i = 0; i < index-1; i++ {
        if node.next != nil {
            node = node.next
        } else {
            return
        }
    }

    node.next = &Node{
        next: node.next,
        val: val,
    }

    return
}


/** Delete the index-th node in the linked list, if the index is valid. */
func (this *MyLinkedList) DeleteAtIndex(index int)  {
    if this.head == nil {
        return
    }
    
    node := this.head
    var i int

    // Iterate to (index - 1) node, if possible
    for i = 0; i < index-1; i++ {
        if node.next != nil {
            node = node.next
        } else {
            return
        }
    }

    if node.next == nil {
        return
    }

    node.next = node.next.next
}


/**
 * Your MyLinkedList object will be instantiated and called as such:
 * obj := Constructor();
 * param_1 := obj.Get(index);
 * obj.AddAtHead(val);
 * obj.AddAtTail(val);
 * obj.AddAtIndex(index,val);
 * obj.DeleteAtIndex(index);
 */