leetcode 23. Merge k Sorted Lists

2019-11-06 07:02:01

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leetcode 23. Merge k Sorted Lists

思路：divide and conquer，分治 code:

#include <iostream>#include <vector>#include <string>#include <queue>using namespace std;/** * Definition for singly-linked list. * struct ListNode { * int val; * ListNode *next; * ListNode(int x) : val(x), next(NULL) {} * }; */// Divide and Conquerclass Solution {public: ListNode* mergeTwoLists(ListNode* l1, ListNode* l2) { if (!l1) return l2; if (!l2) return l1; if (l1->val <= l2->val) { l1->next = mergeTwoLists(l1->next, l2); return l1; } else { l2->next = mergeTwoLists(l1, l2->next); return l2; } } ListNode* mergeKLists(vector<ListNode*>& lists) { if (lists.empty()) return NULL; while (lists.size() > 1) { lists[0] = mergeTwoLists(lists[0], lists.back()); lists.pop_back(); // merge the first and the last, use pop_back() } return lists[0]; }};int main () { return 0;}

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