[LeetCode][JavaScript]Merge k Sorted Lists

Merge k Sorted Lists 

Merge k sorted linked lists and return it as one sorted list. Analyze and describe its complexity.

https://leetcode.com/submissions/detail/28015840/

 

 

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直接使用了“Merge Two Sorted Lists”里写的方法。

http://www.cnblogs.com/Liok3187/p/4514347.html

两两比较就好了，每一轮比较都会减少一半lists的数量。

 

/**
 * Definition for singly-linked list.
 * function ListNode(val) {
 *     this.val = val;
 *     this.next = null;
 * }
 */
/**
 * @param {ListNode[]} lists
 * @return {ListNode}
 */
var mergeKLists = function(lists) {
    function mergeTwoLists(l1, l2) {
        var i = l1, j = l2;
        var res = new ListNode(-1);
        curr = res;
        while(i && j && i.val !== undefined && j.val !== undefined){
            if(i.val < j.val){
                curr.next = i;
                i = i.next;
            }else{
                curr.next = j;
                j = j.next;
            }
            curr = curr.next;     
        }
        if(i && i.val !== undefined){
            curr.next = i;
        }
        if(j && j.val !== undefined){
            curr.next = j;
        }
        return res.next || [];
    }
    
    var k;
    while(lists.length >= 2){
        var tmpList = [];
        for(k = lists.length - 1; k >= 0; k-=2){
            tmpList.push(mergeTwoLists(lists[k], lists[k - 1]));
        }
        if(k === 0){
            tmpList.push(lists[0]);
        }
        lists = tmpList;
    }
    
    return lists[0] || [];
};