[LeetCode-23] 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.

 

嗯……没啥好说的……

 

/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     ListNode *next;
 *     ListNode(int x) : val(x), next(NULL) {}
 * };
 */
class Solution {
    public:
        ListNode *mergeKLists(vector<ListNode *> &lists) {
            // Start typing your C/C++ solution below
            // DO NOT write int main() function
            ListNode* tmp_node = NULL;
            ListNode* tar_node = NULL;
            ListNode* new_node = NULL;
            ListNode* result = NULL;
            for (int i = 0; i < lists.size(); ++i) {
                tmp_node = lists[i];
                if (NULL == tmp_node) {
                    continue;
                }
                if (NULL == result) {
                    result = new ListNode(tmp_node->val);
                    tmp_node = tmp_node->next;
                } else {
            if (result->val > tmp_node->val) {
                new_node = new ListNode(tmp_node->val);
            new_node->next = result;
            result = new_node;
            tmp_node = tmp_node->next;
            }
        }
                tar_node = result;
                while (tmp_node != NULL) {
                    while (NULL != tar_node->next && tar_node->next->val < tmp_node->val) {
                tar_node = tar_node->next;
            }
                    if (NULL == tar_node->next) {
                        new_node = new ListNode(tmp_node->val);
                        tar_node->next = new_node;
                    } else {
                        new_node = new ListNode(tmp_node->val);
                        new_node->next = tar_node->next;
                        tar_node->next = new_node;
                    }
                    tmp_node = tmp_node->next;
                }
            }
            return result;

        }
};