day7:intersection of lists

Author: mandliya

README.md

@@ -8,9 +8,9 @@
 | :------------: | :----------: |
 | Total C++ Problems | 188 |
 | Total Python Problems | 11 |
-| Current Daily Streak| 6 |
+| Current Daily Streak| 7 |
 | Last Streak | 06/20/2019 - 06/21/2019|
-| Current Streak | 06/23/2019 - 06/28/2019|
+| Current Streak | 06/23/2019 - 06/29/2019|
 
 </center>
 
@@ -29,7 +29,7 @@
 | Print middle node of linkedlist without iterating twice. | [printMiddleNode.cpp](linked_list_problems/printMiddleNode.cpp) | | Detecting and removing a cycle in linkedlist.| [floyedCycleDetection.cpp](linked_list_problems/floyedCycleDetection.cpp)|
 | Determine if a linked list is a pallindrome. | [listPallindrome.cpp](linked_list_problems/listPallindrome.cpp) |
 | Insert data in a sorted linked list.|[insertInASortedLinkedList.cpp](linked_list_problems/insertInASortedLinkedList.cpp) |
-| Determine the intersection(merging) point of two given linked list.| [findIntersectionPointOfLists.cpp](linked_list_problems/findIntersectionPointOfLists.cpp)|
+| Determine the intersection(merging) point of two given linked list.| [findIntersectionPointOfLists.cpp](linked_list_problems/findIntersectionPointOfLists.cpp), [intersection_of_lists.py](linked_list_problems/intersection_of_lists.py)|
 | Clone a linkedlist which has next and an random pointer, Space Complexity - O(1). | [cloneListWithRandomPtr.cpp](linked_list_problems/cloneListWithRandomPtr.cpp), [clone_list_with_random_ptr.py](linked_list_problems/clone_list_with_random_ptr.py)|
 | Given a sorted linked list with duplicates, remove duplicates in one iteration. | [removeDuplicatesFromSortedList.cpp](linked_list_problems/removeDuplicatesFromSortedList.cpp)| 
 | Using Floyd's cycle finding algorithm, detect if a linkedlist contain cycle, if it does contain cycle, remove the loop | [floyedCycleDetection.cpp](linked_list_problems/floyedCycleDetection.cpp) |

linked_list_problems/intersection_of_lists.py

@@ -0,0 +1,81 @@
+"""
+Given two linked lists, they both merge at some point.
+Find out the merging point
+
+1-->2-->3-->4-->5
+        ^
+        |
+7-->8-->9
+
+List 1 and List 2 intereset at 3
+"""
+
+class Node:
+    def __init__(self, data):
+        """Represents a linked list node."""
+        self.next = None
+        self.data = data
+
+    def print(self):
+        """Prints the node's data with its address."""
+        print(self.data, '(', hex(id(self)), ')', end=' ')
+
+def len(head):
+    """Length of the list."""
+    count = 0
+    itr = head
+    while itr:
+        count += 1
+        itr = itr.next
+    return count
+
+def intersect(head1, head2):
+    len1 = len(head1)
+    len2 = len(head2)
+    smaller = head1 if len1 < len2 else head2
+    larger = head1 if len1 > len2 else head2
+
+    diff = abs(len1-len2)
+    i = 0
+    while larger and i < diff:
+        i += 1
+        larger = larger.next
+
+    itr1 = smaller
+    itr2 = larger
+    while itr1 and itr2:
+        if itr1 == itr2:
+            return itr1
+        itr1 = itr1.next
+        itr2 = itr2.next
+    return None
+
+def print_list(node):
+    while node:
+        node.print()
+        print('-->', end=' ')
+        node = node.next
+    print('None')
+
+
+if __name__ == "__main__":
+    head = Node(1)
+    head.next = Node(2)
+    head.next.next = Node(3)
+    head.next.next.next = Node(4)
+    head.next.next.next.next = Node(5)
+
+    print("List 1:")
+    print_list(head)
+
+    head2 = Node(7)
+    head2.next = Node(8)
+    head2.next.next = Node(9)
+    head2.next.next.next = head.next.next
+
+    print("List 2:")
+    print_list(head2)
+
+    print("Intersection of list1 and list2:")
+    intersect(head, head2).print()
+