leetcode/algorithms/MergeTwoSortedLists/solution.js at master · P-ppc/leetcode · GitHub

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/**
 * 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) {
    let head = res = null

    while (l1 !== null && l2 !== null) {
        if (res === null) {
            head = res = new ListNode(Math.min(l1.val, l2.val))
        } else {
            head.next = new ListNode(Math.min(l1.val, l2.val))
            head = head.next
        }
        if (l1.val <= l2.val) {
            l1 = l1.next
        } else {
            l2 = l2.next
        }
    }

    if (res === null) {
        res = l1 !== null ? l1 : l2
    } else {
        head.next = l1 !== null ? l1 : l2
    }

    return res
};