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solution148.cpp
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89 lines (79 loc) · 1.75 KB
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/**
* Sort List
*
* cpselvis([email protected])
* Oct 16th, 2016
*/
#include<iostream>
using namespace std;
struct ListNode {
int val;
ListNode *next;
ListNode(int x) : val(x), next(NULL) {}
};
class Solution {
public:
ListNode* sortList(ListNode* head) {
if (head == NULL || head -> next == NULL)
return head;
ListNode *slow = head;
ListNode *fast = head;
ListNode *pre = NULL;
while (fast && fast -> next)
{
pre = slow;
slow = slow -> next;
fast = fast -> next -> next;
}
pre -> next = NULL;
ListNode *l1 = sortList(head);
ListNode *l2 = sortList(slow);
return merge(l1, l2);
}
ListNode *merge(ListNode *head1, ListNode *head2)
{
if (head1 == NULL) return head2;
if (head2 == NULL) return head1;
ListNode *dummy = new ListNode(-1);
ListNode *newHead = dummy;
while (head1 != NULL && head2 != NULL)
{
if (head1 -> val < head2 -> val)
{
newHead -> next = head1;
head1 = head1 -> next;
}
else
{
newHead -> next = head2;
head2 = head2 -> next;
}
newHead = newHead -> next;
}
if (head1 != NULL)
{
newHead -> next = head1;
}
else if (head2 != NULL)
{
newHead -> next = head2;
}
return dummy -> next;
}
};
int main(int argc, char **argv)
{
ListNode *head = new ListNode(1);
head -> next = new ListNode(3);
head -> next -> next = new ListNode(5);
head -> next -> next -> next = new ListNode(2);
head -> next -> next -> next -> next = new ListNode(4);
head -> next -> next -> next -> next -> next = new ListNode(6);
Solution s;
ListNode *newHead = s.sortList(head);
while (newHead != NULL)
{
cout << newHead -> val << endl;
newHead = newHead -> next;
}
}