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Commit a2444f2

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day4: python prob 9
1 parent 1720188 commit a2444f2

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‎README.md

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| Current Status| Stats |
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| :------------: | :----------: |
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| Total C++ Problems | 188 |
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| Total Python Problems | 8 |
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| Current Daily Streak| 3 |
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| Total Python Problems | 9 |
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| Current Daily Streak| 4 |
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| Last Streak | 06/20/2019 - 06/21/2019|
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| Current Streak | 06/23/2019 - 06/25/2019|
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| Current Streak | 06/23/2019 - 06/26/2019|
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</center>
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| Find the nth node of linked list from last. |[nthToLastNode.cpp](linked_list_problems/nthToLastNode.cpp), [nth_to_last_node.py](linked_list_problems/nth_to_last_node.py) |
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| Add numbers where each digit of the number is represented by node of a linkedlist. Give output as a linked list. | [add_two_numbers_lists.cpp](linked_list_problems/add_two_numbers_lists.cpp), [add_two_numbers_list.py](linked_list_problems/add_two_numbers_lists.py)|
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| Swap nodes of a linkedlist without swapping data. |[swapNodesWithoutSwappingData.cpp](linked_list_problems/swapNodesWithoutSwappingData.cpp), [swap_nodes_without_swapping_data.py](linked_list_problems/swap_nodes_without_swapping_data.py)|
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| Reverse a linked list, iteratively and recursively | [reverseLinkedListIterAndRecurse.cpp](linked_list_problems/reverseLinkedListIterAndRecurse.cpp)|
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| Reverse a linked list, iteratively and recursively | [reverseLinkedListIterAndRecurse.cpp](linked_list_problems/reverseLinkedListIterAndRecurse.cpp), [reverse_linkedlist.py](linked_list_problems/reverse_linkedlist.py)|
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| Given a linked list, reverse alternate nodes and append at the end. | [reverseAlternateNodes.cpp](linked_list_problems/reverseAlternateNodes.cpp) |
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| Only given a node pointer, delete the node from the linked list. | [deleteNode.cpp](linked_list_problems/deleteNode.cpp)|
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| Delete the entire linkedlist. | [deleteLinkedlist.cpp](linked_list_problems/deleteLinkedlist.cpp)|
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"""
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Reverse a linked list
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"""
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class Node:
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"""Representation of a linked list node"""
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def __init__(self, data):
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self.data = data
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self.next = None
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class LinkedList:
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"""Representation of a linked list"""
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def __init__(self):
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self.head = None
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def push(self, data):
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"""Pushes a new node with data at the head of the list"""
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new_node = Node(data)
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new_node.next = self.head
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self.head = new_node
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def print(self):
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"""Prints the linked list"""
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itr = self.head
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while itr:
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if itr.next is None:
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print(itr.data)
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else:
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print(str(itr.data), '-->', end=' ')
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itr = itr.next
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def _reverse_recur(self, node):
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"""Utility function to recursively reverse a list"""
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if node is None:
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return
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if node.next is None:
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self.head = node
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return
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first = node
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rest = node.next
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self._reverse_recur(rest)
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first.next.next = first
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first.next = None
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def reverse_r(self):
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"""Recursively reverses a list"""
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self._reverse_recur(self.head)
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def reverse_i(self):
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"""Iteratively reverses a list"""
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if (self.head is None) or \
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(self.head and self.head.next is None):
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return
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prev = None
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curr = self.head
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new_head = None
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while curr:
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prev = curr
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curr = curr.next
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prev.next = new_head
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new_head = prev
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self.head = new_head
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if __name__ == "__main__":
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ll = LinkedList()
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ll.push(5)
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ll.push(4)
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ll.push(3)
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ll.push(2)
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ll.push(1)
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ll.print()
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ll.reverse_i()
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ll.print()
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ll.reverse_r()
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ll.print()

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