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merge_k_sorted_lists.js
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merge_k_sorted_lists.js
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/*
Merge k Sorted Lists
https://leetcode.com/problems/merge-k-sorted-lists/
Merge k sorted linked lists and return it as one sorted list. Analyze and describe its complexity.
Example:
Input:
[
1->4->5,
1->3->4,
2->6
]
Output: 1->1->2->3->4->4->5->6
*/
var mergeKLists = function (lists) {
if (lists.length === 0) return null;
var queue = [];
var list1;
var list2;
for (var i = 0; i < lists.length; i++) queue.push(lists[i]);
while (queue.length > 1) {
list1 = queue.shift();
list2 = queue.shift();
queue.push(mergeLists(list1, list2));
}
return queue.shift();
};
var mergeLists = function (list1, list2) {
if (list1 === null) {
return list2;
} else if (list2 === null) return list1;
var iter1 = list1;
var iter2 = list2;
var head;
if (iter1.val < iter2.val) {
head = iter1;
iter1 = iter1.next;
} else {
head = iter2;
iter2 = iter2.next;
}
var iterHead = head;
while (iter1 !== null && iter2 !== null) {
if (iter1.val < iter2.val) {
iterHead.next = iter1;
iter1 = iter1.next;
} else {
iterHead.next = iter2;
iter2 = iter2.next;
}
iterHead = iterHead.next;
iterHead.next = null;
}
if (iter1 !== null) {
iterHead.next = iter1;
} else if (iter2 !== null) {
iterHead.next = iter2;
}
return head;
};
module.exports.mergeKLists = mergeKLists;