来源：力扣（LeetCode） 链接：https://leetcode.cn/problems/merge-k-sorted-lists 著作权归领扣网络所有。商业转载请联系官方授权，非商业转载请注明出处。

给你一个链表数组，每个链表都已经按升序排列。
请你将所有链表合并到一个升序链表中，返回合并后的链表。

解答

/**
 * Definition for singly-linked list.
 * function ListNode(val, next) {
 *     this.val = (val===undefined ? 0 : val)
 *     this.next = (next===undefined ? null : next)
 * }
 */
/**
 * @param {ListNode[]} lists
 * @return {ListNode}
*/
const findMinValChain = (lists) => {
    let min = Infinity,
        minIdx = -1;
    for (let i = 0; i < lists.length; i++) {
        const head = lists[i];
        if (head && min > head.val) {
            min = head.val;
            minIdx = i;
        }
    }
    return minIdx;
}
var mergeKLists = function(lists) {
    let head = new ListNode(),
        prev = head;
    while (lists.length) {
        let chainIdx = findMinValChain(lists),
        chainHead = lists[chainIdx];
        if (!chainHead) {
            lists.splice(chainIdx, 1);
            continue;
        }
        prev.next = chainHead;
        prev = prev.next;
        if (chainHead && chainHead.next) {
            lists[chainIdx] = chainHead.next;
            chainHead.next = null;
        } else {
            lists.splice(chainIdx, 1);
        }
    }
    return head.next;
};