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Commit 6175022

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streak day 1: swap nodes without data in linkedlist py
1 parent 0a86814 commit 6175022

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3 files changed

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‎README.md

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@@ -6,9 +6,11 @@
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| Current Status| Stats |
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| :------------: | :----------: |
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| Total Problems | 188 |
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| Current Daily Streak| 2 |
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| Last updated | 06/21/2019|
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| Total C++ Problems | 188 |
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| Total Python Problems | 5 |
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| Current Daily Streak| 1 |
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| Last Streak | 06/20/2019 - 06/21/2019|
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| Current Streak | 06/23/2019 - |
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</center>
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@@ -19,7 +21,7 @@
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| :------------ | :----------: |
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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)|
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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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| 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)|

‎linked_list_problems/swapNodesWithoutSwappingData.cpp

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -60,7 +60,7 @@ void swapSpecial(Node* & head, int x, int y) {
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if ( prevy != nullptr) {
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prevy->next = currx;
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} else {
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head = curry;
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head = currx;
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}
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//now lets swap the next pointers
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# Problem : Given a linked list, and two data values, x and y.
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# Goal: Swap the nodes of linkedlist by swapping pointers
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# (and not swapping data) such that nodes with data x will contain y and vice versa.
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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 new data to 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_list(self):
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"""Prints a 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 swap_nodes_without_swapping_data(self, x, y):
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"""Swap the nodes of linked without swapping pointers i.e.
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swap nodes such that nodes with data x will contain y and vice versa."""
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# We are making assumption that nodes in linked list are unique
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if x == y:
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return
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curr_x = self.head
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curr_y = self.head
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prev_x = None
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prev_y = None
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# find node with data x
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while curr_x and curr_x.data != x:
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prev_x = curr_x
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curr_x = curr_x.next
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# find node with data y
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while curr_y and curr_y.data != y:
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prev_y = curr_y
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curr_y = curr_y.next
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# x or y is not there
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if curr_x is None or curr_y is None:
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return
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# if x is not head of the linked list.
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if prev_x is not None:
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prev_x.next = curr_y
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else: # if x was head, make y the head of the linked list.
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self.head = curr_y
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# if y is not head of the linked list
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if prev_y is not None:
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prev_y.next = curr_x
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else: # if y was head, make x the head of the linked list.
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self.head = curr_x
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# now swap the next pointers.
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temp = curr_x.next
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curr_x.next = curr_y.next
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curr_y.next = temp
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if __name__ == "__main__":
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lst = LinkedList()
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lst.push(5)
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lst.push(1)
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lst.push(3)
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lst.push(2)
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lst.push(4)
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print("List before:")
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lst.print_list()
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lst.swap_nodes_without_swapping_data(1, 4)
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print("List after:")
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lst.print_list()

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