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23.merge-k-sorted-lists.cpp
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23.merge-k-sorted-lists.cpp
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/*
* @lc app=leetcode id=23 lang=cpp
*
* [23] Merge k Sorted Lists
*/
// @lc code=start
/**
* Definition for singly-linked list.
* struct ListNode {
* int val;
* ListNode *next;
* ListNode() : val(0), next(nullptr) {}
* ListNode(int x) : val(x), next(nullptr) {}
* ListNode(int x, ListNode *next) : val(x), next(next) {}
* };
*/
class Solution {
public:
ListNode* merge(ListNode* a, ListNode *b) {
ListNode dummy;
ListNode *curr=&dummy;
while(a&&b) {
if (a->val<b->val) {
curr->next=a;
a=a->next;
} else {
curr->next=b;
b=b->next;
}
curr=curr->next;
}
if (a) {
curr->next=a;
} else {
curr->next=b;
}
return dummy.next;
}
ListNode* mergeKLists(vector<ListNode*>& lists) {
int n=lists.size();
int i;
int interval=1;
if (n==0) return NULL;
while(interval<n) {
for(i=0;i<n-interval;i=i+interval*2) {
lists[i]=merge(lists[i],lists[i+interval]);
}
interval*=2;
}
return lists[0];
}
};
// @lc code=end