#23 Merge k Sorted Lists

Title Link: 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.

/** * Definition for singly-linked list. * struct ListNode {* int val; * struct ListNode *next; *}; */void percolateup (struct listnode** lists, int i) {//Pre I elements are already ordered, upper filter i+1 element struct listnode* tmp = lists[i];while (i > 0 && lists[(i-1)/2]->val > Tmp->val) {//element to the root node path all nodes larger than that element are moved down lists[i] = lists[(i-1)/2];i = (i-1 )/2;} Lists[i] = tmp;} int buildheap (struct listnode** lists, int k) {int i, size = 0;for (i = 0; i < K; ++i)//insert non-empty element into heap if (Lists[i]) {lists [Size] = Lists[i];p ercolateup (lists, size); ++size;} return size;} Only the top elements of the heap are not in order to be filtered; that is, the smaller son is constantly moved to the hole until the younger one is not less than the heap top element void Percolatedown (struct listnode** lists, int size) {struct listnode* TMP = Lists[0];int i = 0, Smallchild = 2 * i + 1;//first record left son for smaller son, if right son smaller, update if (Smallchild + 1 < size && Lists[sma Llchild]->val > Lists[smallchild + 1]->val) ++smallchild;while (Smallchild < size && lists[ Smallchild]->val < Tmp->val) {Lists[i] = Lists[smallchild];i = Smallchild;smallChild = 2 * i + 1;if (smallchild + 1 < size && Lists[smallchild]->val > lists[smallchild + 1]->val) ++s Mallchild;} Lists[i] = tmp;} Heap implementation Priority queue, the first element of the K list is built heap, each popup heap top element;//delete heap top element after refactoring requires log (k) operation, total time complexity n*log (k) struct listnode* mergeklists (struct listnode** Lists, int listssize) {if (lists = = NULL | | listssize <= 0) return null;if (listssize = 1) return Lists[0];int Size;stru CT listnode* head = (struct ListNode *) malloc (sizeof (struct listnode));//Dummy node struct listnode* p = head;head->next = NULL ;//must not be small, otherwise all the list is empty can not return nullsize = buildheap (lists, listssize),//will lists sorted by the heap, and return the initial heap size, that is, the number of non-empty list while (size) {///As long as the heap is not empty, Each pop-up heap top element, update heap P->next = lists[0];p = p->next;lists[0] = lists[0]->next;//Update heap top element if (lists[0] = null) {//if the top element of the heap is empty, Move the trailing element to the top of the heap lists[0] = lists[size-1];--size;} Percolatedown (lists, size);//The top element of the filter heap keeps the heap order}p = Head->next;free (head); return p;}

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#23 Merge k Sorted Lists