DSA Interview Challenges

Reverse Linked List

Iterating through the list and reversing the direction of the next pointers of the nodes.
After the entire list is reversed, the head pointer is updated to point to the new head of the list, which was the original tail.


/**
/**
 * Definition for singly-linked list.
 * function ListNode(val, next) {
 *     this.val = (val===undefined ? 0 : val)
 *     this.next = (next===undefined ? null : next)
 * }
 */
/**
 * @param {ListNode} head
 * @return {ListNode}
 */
var reverseList = function(head) {
    let prev = null,curr=head,next=null
    while(curr!=null){
        next = curr.next;
        curr.next = prev;
        prev = curr;
        curr = next;
    }
    head = prev;
    return head;
};

Complexity

Time: O(n)
Space: O(1)

Delete Node in a Linked List

Copy the data from the successor node into the current node to be deleted.
Update the next pointer of the current node to reference the next pointer of the successor node.


/**
 * Definition for singly-linked list.
 * function ListNode(val) {
 *     this.val = val;
 *     this.next = null;
 * }
 */
/**
 * @param {ListNode} node
 * @return {void} Do not return anything, modify node in-place instead.
 */
var deleteNode = function(node) {
node.val=node.next.val;
node.next=node.next.next;
};

Complexity

Time: O(1)
Space: O(1)