剑指offer系列算法

1 . Reverse Linked List

/**
 1. Definition for singly-linked list.
 2. function ListNode(val) {
 3.     this.val = val;
 4.     this.next = null;
 5. }
 */
/**
 6. @param {ListNode} head
 7. @return {ListNode}
 */
var reverseList = function(head) {
    var currNode = head;
    var prevNode = null;
    var nextNode = null;
    while(currNode != null){
        nextNode = currNode.next;
        currNode.next = prevNode;
        prevNode = currNode;
        currNode = nextNode;
    }
    return prevNode;
};

2 . Merge Two Sorted Lists
Merge two sorted linked lists and return it as a new list. The new list should be made by splicing together the nodes of the first two lists.

/**
 * Definition for singly-linked list.
 * function ListNode(val) {
 *     this.val = val;
 *     this.next = null;
 * }
 */
/**
 * @param {ListNode} l1
 * @param {ListNode} l2
 * @return {ListNode}
 */
var mergeTwoLists = function(l1, l2) {
    var dummy = new ListNode(0);
    var curr = dummy;
    while(l1 != null && l2 != null){
        if(l1.val >= l2.val){
            curr.next = l2;
            l2 = l2.next;
        }else{
            curr.next = l1;
            l1 = l1.next;
        }
        curr = curr.next;
    }
    if(l1 != null){
        curr.next = l1;
    }
    if(l2 != null){
        curr.next = l2;
    }
    return dummy.next;
};