LeetCode #147 Insertion Sort List

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Problem

Sort a linked list using insertion sort.

img
A graphical example of insertion sort. The partial sorted list (black) initially contains only the first element in the list.
With each iteration one element (red) is removed from the input data and inserted in-place into the sorted list

Algorithm of Insertion Sort:

  1. Insertion sort iterates, consuming one input element each repetition, and growing a sorted output list.
  2. At each iteration, insertion sort removes one element from the input data, finds the location it belongs within the sorted list, and inserts it there.
  3. It repeats until no input elements remain.

Examples

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Input: 4->2->1->3
Output: 1->2->3->4
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Input: -1->5->3->4->0
Output: -1->0->3->4->5

Method:

Time Complexity:

Space Complexity:

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# Definition for singly-linked list.
# class ListNode:
#     def __init__(self, x):
#         self.val = x
#         self.next = None

class Solution:
    def print(self, head):
        ptr = head
        while ptr:
            print(ptr.val, end=' ')
            ptr = ptr.next
        
        print('\n')
    def helper()

    def insertionSortList(self, head):
        """
        :type head: ListNode
        :rtype: ListNode
        """
        if not head:
            return head

        dummy = ListNode(float('-inf'))
        dummy.next = head
        cur = head
        
        while cur.next:
            if cur.val <= cur.next.val:
                cur = cur.next
            else:
                ptr = dummy
                small = cur.next.val
                while ptr.next != cur and ptr.next.val < small:
                    ptr = ptr.next

                tmp = cur.next
                cur.next = tmp.next
                tmp.next = cur
                ptr.next = tmp
                self.print(dummy)
                # cur = dummy.next

        
        return dummy.next

Solution2

Method:

Time Complexity:

Space Complexity:

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# Definition for singly-linked list.
# class ListNode:
#     def __init__(self, x):
#         self.val = x
#         self.next = None

class Solution:
    def insertionSortList(self, head):
        cur = dummy = ListNode(0)
        while head:
            if cur and cur.val > head.val: 
                cur = dummy
            while cur.next and cur.next.val < head.val:
                cur = cur.next
            cur.next, cur.next.next, head = head, cur.next, head.next
        return dummy.next