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‎.ipynb_checkpoints/README-checkpoint.md‎

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@@ -44,13 +44,14 @@ Elements of Programming Interviews in Python, by Adnan Aziz, Tsung-Hsien Lee, an
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- [Build a Linked List](07_linkedList/buildLinkedList.ipynb)
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- 7: [Linked Lists Boot Camp](07_linkedList/linkedListBootCamp.ipynb)
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- 7.1: [Merge Two Sorted Lists](07_linkedList/mergeTwoSortedLists.ipynb)
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- 7.2:
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- 7.2: [Reverse a Single Sublist](07_linkedList/reverseSublist.ipynb)
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### [Ch. 10 Heaps](10_Heaps)
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- 10: [Heap Boot Camp](10_Heaps/heapBootCamp.ipynb)
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- 10.1: [Merge Sorted Files](10_Heaps/mergeSortedFiles2.ipynb)
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- 10.2: [Sort an Inreasing-Decreasing Array](10_Heaps/sortIncreaseDecrease.ipynb)
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- 10.3: [Sort an Almost-Sorted Array](10_Heaps/sortAlmostSorted.ipynb)
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- 10.4: [Compute the K Closest Stars](10_Heaps/kClosestStars.ipynb)
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### [Ch. 13: Sorting](13_sorting)

‎07_linkedList/.ipynb_checkpoints/reverseSublist-checkpoint.ipynb‎

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{
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"cells": [
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{
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"cell_type": "markdown",
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"id": "f6737794-c5b1-44dc-83e6-149a1a6987fb",
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"metadata": {},
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"source": [
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"# **7.2 Reverse a Single Sublist**\n",
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"---\n",
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"- Reversing a sublist within a list \n",
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"- Input = singly linked list `L` and two integers `s` and `f`\n",
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"- Reverse nodes from `s` to `f` INCLUSIVE\n",
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"- Succesor fields also have to be updated \n",
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"- Iterate through list until you hit `s` and predecessor \n",
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"- `s` node begins reversal process and we count until we reach `f`\n",
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"- Relink reversed sublist with rest of sublist \n"
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]
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},
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{
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"cell_type": "code",
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"execution_count": 1,
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"id": "780e7092-9cf1-4789-9b81-c8885169e3f0",
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"metadata": {},
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"outputs": [],
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"source": [
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"from typing import List\n",
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"from typing import Optional"
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]
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},
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{
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"cell_type": "markdown",
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"id": "bcec5090-22a3-4e56-b068-2227e12f4b0a",
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"metadata": {},
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"source": [
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"---\n",
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"## Reverse Sublist"
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]
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},
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{
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"cell_type": "raw",
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"id": "7ec845cd-10ae-4d74-be3a-3b3aba23d346",
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"metadata": {
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"tags": []
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},
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"source": [
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" def reverse_sub(self, start: int, finish: int) -> Optional[ListNode]:\n",
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" \n",
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" sentinel = sublist_head = ListNode(0,L)\n",
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" \n",
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" for _ in range(1,start):\n",
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" sublist_head = sublist_head.next\n",
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" \n",
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" # Revese\n",
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" sublist_itr = sublist_head.next\n",
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" for _ in range(finish - start):\n",
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" temp = sublist_itr.next\n",
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" sublist_itr, temp.next = sublist_head.next = (temp.next, sublist_head.next, temp)\n",
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" \n",
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" return sentinel.next \n",
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" "
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]
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},
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{
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"cell_type": "code",
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"execution_count": 4,
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"id": "01ccfdba-950e-4eee-ad34-19f72e3814a1",
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"metadata": {},
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"outputs": [
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{
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"name": "stdout",
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"output_type": "stream",
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"text": [
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"10 20 30 40 50 60 70 \n",
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"10 20 60 50 40 30 70 \n"
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]
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}
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],
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"source": [
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"class Node:\n",
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" def __init__(self, data):\n",
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" self.data = data\n",
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" self.next = None\n",
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" \n",
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"# goes with reverse subllist function\n",
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"def reverse(head):\n",
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" prev = None \n",
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" curr = head\n",
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" while (curr):\n",
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" next = curr.next\n",
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" curr.next = prev\n",
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" prev = curr\n",
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" curr = next\n",
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" return prev\n",
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"\n",
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"def reverseBetween(head, m, n):\n",
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" if (m == n):\n",
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" return head \n",
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" revs = None\n",
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" revs_prev = None\n",
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" revend = None\n",
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" revend_next = None\n",
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" i = 1\n",
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" curr = head\n",
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" while (curr and i <= n):\n",
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" if (i < m):\n",
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" revs_prev = curr\n",
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" if (i == m):\n",
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" revs = curr\n",
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" if (i == n):\n",
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" revend = curr\n",
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" revend_next = curr.next\n",
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" curr = curr.next\n",
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" i += 1\n",
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" revend.next = None\n",
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" revend = reverse(revs)\n",
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" if (revs_prev):\n",
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" revs_prev.next = revend\n",
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" else:\n",
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" head = revend\n",
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" revs.next = revend_next\n",
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" return head\n",
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" \n",
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"def prints(head):\n",
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" while (head != None):\n",
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" print(head.data, end = ' ')\n",
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" head = head.next\n",
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" print()\n",
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" \n",
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"def push(head_ref, new_data):\n",
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" \n",
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" new_node = Node(new_data)\n",
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" new_node.data = new_data\n",
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" new_node.next = (head_ref)\n",
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" (head_ref) = new_node\n",
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" return head_ref\n",
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" \n",
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" \n",
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"if __name__=='__main__':\n",
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" \n",
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" head = None\n",
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" head = push(head, 70)\n",
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" head = push(head, 60)\n",
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" head = push(head, 50)\n",
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" head = push(head, 40)\n",
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" head = push(head, 30)\n",
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" head = push(head, 20)\n",
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" head = push(head, 10)\n",
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" prints(head)\n",
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" \n",
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" reverseBetween(head, 3, 6)\n",
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" prints(head)"
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]
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},
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{
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"cell_type": "markdown",
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"id": "518235a2-eea3-467b-92eb-e9e3e420fc31",
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"metadata": {},
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"source": [
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"##### Time Complexity: `O(f)`\n",
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"- `f` = end of reversal range "
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]
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},
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{
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"cell_type": "markdown",
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"id": "69520395-ba3d-4d90-99cd-37f90b59c4d4",
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"metadata": {},
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"source": [
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"---\n",
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"# Variant\n",
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"#### Reverse a Singly Linked List in Constant Space"
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]
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},
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{
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"cell_type": "code",
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"execution_count": 5,
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"id": "096fd3d5-c899-4c4a-95d0-8d348264e349",
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"metadata": {},
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"outputs": [],
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"source": [
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"class ListNode:\n",
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" def __init__(self, data=None, next=None):\n",
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" self.data = data\n",
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" self.next = next "
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]
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},
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{
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"cell_type": "code",
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"execution_count": 6,
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"id": "464e4a49-b810-47ef-a6de-ab1c94c77b42",
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"metadata": {
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"tags": []
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},
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"outputs": [],
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"source": [
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"class LinkedList:\n",
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" def __init__(self):\n",
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" self.head = None\n",
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" self.last_node = None\n",
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" \n",
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" def insert_at_beg(self,data):\n",
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" # inserting at beginning -> next element is the current head \n",
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" node = ListNode(data,self.head)\n",
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" self.head = node \n",
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" \n",
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" def reverse(self):\n",
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" prev = None\n",
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" current = self.head\n",
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" while(current is not None):\n",
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" next = current.next\n",
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" current.next = prev\n",
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" prev = current \n",
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" current = next\n",
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" self.head = prev \n",
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" \n",
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" def print(self):\n",
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" if self.head is None:\n",
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" print(\"Linked List is empty\")\n",
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" return\n",
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" itr = self.head\n",
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" llstr = ''\n",
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" while itr:\n",
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" llstr += str(itr.data) + '-->'\n",
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" itr = itr.next\n",
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" print(llstr)\n",
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" "
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]
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},
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{
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"cell_type": "code",
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"execution_count": 7,
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"id": "635234a5-66d8-4480-a374-e8ec2c5f645d",
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"metadata": {},
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"outputs": [
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{
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"name": "stdout",
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"output_type": "stream",
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"text": [
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"60-->50-->40-->30-->20-->10-->\n",
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"10-->20-->30-->40-->50-->60-->\n"
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]
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}
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],
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"source": [
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"if __name__ == '__main__':\n",
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" ll = LinkedList()\n",
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" ll.insert_at_beg(10)\n",
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" ll.insert_at_beg(20)\n",
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" ll.insert_at_beg(30)\n",
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" ll.insert_at_beg(40)\n",
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" ll.insert_at_beg(50)\n",
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" ll.insert_at_beg(60)\n",
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" ll.print()\n",
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" ll.reverse()\n",
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" ll.print()"
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]
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},
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{
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"cell_type": "markdown",
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"id": "667a798a-e1c2-43cb-843b-ebe7d442ea48",
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"metadata": {},
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"source": [
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"---\n",
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"# Variant\n"
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]
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},
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{
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"cell_type": "code",
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"execution_count": null,
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"id": "ed015ff1-09ae-4bc9-b2de-417a36c6614a",
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"metadata": {},
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"outputs": [],
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"source": []
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}
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],
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"metadata": {
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"kernelspec": {
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"display_name": "Python 3",
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"language": "python",
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"name": "python3"
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},
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"language_info": {
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"codemirror_mode": {
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"name": "ipython",
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"version": 3
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},
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"file_extension": ".py",
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"mimetype": "text/x-python",
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"name": "python",
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"nbconvert_exporter": "python",
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"pygments_lexer": "ipython3",
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"version": "3.8.8"
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}
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},
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"nbformat": 4,
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"nbformat_minor": 5
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}

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