added test95 which finds the intersection of two linked lists in O(N)…

… time and O(1) memory

README.md

@@ -95,4 +95,5 @@
 * test91 - sorts a linkled list by using insertion sort
 * test92 - finds subsets of a list of distinct integers and returns them in the non-descending order
 * test93 - creates a list with only unique items
-* test94 - approximates the Pi value by accumulating the distance among point increments on the upper right quartile of the circle 
+* test94 - approximates the Pi value by accumulating the distance among point increments on the upper right quartile of the circle 
+* test95 - finds the intersection of two linked lists in O(N) time and O(1) memory

test95/main.py

@@ -0,0 +1,246 @@
+# This script finds the intersection of two linked lists in O(N) time and O(1) memory
+#
+# This script is a part of the Easy Python project which creates a number
+# sample python scripts to answer simple programming questions. The
+# entire project is accessible at https://github.com/okany/easypython.
+# Copyright (c) 2021 Okan Yilmaz
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <https://www.gnu.org/licenses/>.
+#
+class linkNode():
+    def __init__(self, value):
+        self.value = value
+        self.next = None
+
+class linkedList():
+    def __init__(self, llist, debug = False):
+        self.llist = llist
+        self.debug = debug
+        self.head = self.create_linked_list()
+        if self.debug:
+            self.print()
+
+    def create_linked_list(self):
+        head = None
+
+        if self.llist == None or self.llist == []:
+            pass
+        else:
+            head = prev = linkNode(self.llist[0])
+            if self.debug:
+                print("({})".format(head.value), end="")
+
+            for item in self.llist[1:]:
+                if self.debug:
+                    print("->", end="")
+                prev.next = linkNode(item)
+                prev = prev.next
+                if self.debug:
+                    print("({})".format(prev.value), end="")
+
+        return head
+
+    def append_list(self, list2):
+        if self.head == None:
+            self.head = list2.head
+            return
+
+        current = self.head
+        while current.next:
+            current = current.next
+
+        current.next = list2.head
+
+    def print(self):
+
+        current = None
+        if self.head == None:
+            print("Nil", end="")
+        else:
+            current = self.head
+            while current:
+                print("({})".format(current.value), end ="")
+                current = current.next
+                if(current):
+                    print("->", end="")
+
+        print()
+
+class intersection():
+    def __init__(self, list1, list2):
+        self.list1 = list1
+        self.list2 = list2
+        self.len1 = self.len(list1)
+        self.len2 = self.len(list2)
+
+    def len(self, alist):
+        length = 0
+        current = alist.head
+        while current:
+            current = current.next
+            length += 1
+
+        return length
+
+    def intersect(self):
+        ind1 = ind2 = 0
+        current1 = self.list1.head
+        current2 = self.list2.head
+        if(self.len1 > self.len2):
+            dif = self.len1 - self.len2
+            while dif != 0:
+                current1 = current1.next
+                dif -= 1
+        elif(self.len1 < self.len2):
+            dif = self.len2 - self.len1
+            while dif != 0:
+                current2 = current2.next
+                dif -= 1
+
+        while current1 and current2:
+            if current1.value == current2.value:
+                # we found the intersection node
+                return current1.value
+            else:
+                current1 = current1.next
+                current2 = current2.next
+
+        # current1 and current2 must be Nil
+        return None
+
+if __name__=="__main__":
+
+    tno = 0
+
+    tno += 1
+    debug = False
+    l1 = [1, 2, 3, 4, 5]
+    l2 = [15, 14, 13, 12]
+    lint = [6, 7, 8, 9, 10, 11]
+
+    ll1 = linkedList(l1, debug)
+    ll2 = linkedList(l2, debug)
+    llint = linkedList(lint, debug)
+
+    ll1.append_list(llint)
+    ll2.append_list(llint)
+
+    print("------------------------------------------------------------")
+    print("TEST#{} List #1:".format(tno))
+    ll1.print()
+
+    print("TEST#{} List #2:".format(tno))
+    ll2.print()
+
+    inter = intersection(ll1, ll2)
+
+    print("TEST#{} intersection = {}".format(tno, inter.intersect()))
+    print("------------------------------------------------------------")
+
+    tno += 1
+    debug = False
+    l1 = [2, 3]
+    l2 = [15, 14, 13, 12]
+    lint = [7, 8, 9, 10, 11]
+
+    ll1 = linkedList(l1, debug)
+    ll2 = linkedList(l2, debug)
+    llint = linkedList(lint, debug)
+
+    ll1.append_list(llint)
+    ll2.append_list(llint)
+
+    print("TEST#{} List #1:".format(tno))
+    ll1.print()
+
+    print("TEST#{} List #2:".format(tno))
+    ll2.print()
+
+    inter = intersection(ll1, ll2)
+
+    print("TEST#{} intersection = {}".format(tno, inter.intersect()))
+    print("------------------------------------------------------------")
+
+    tno += 1
+    debug = False
+    l1 = []
+    l2 = [15, 14, 13, 12]
+    lint = [5, 6, 7, 8, 9, 10, 11]
+
+    ll1 = linkedList(l1, debug)
+    ll2 = linkedList(l2, debug)
+    llint = linkedList(lint, debug)
+
+    ll1.append_list(llint)
+    ll2.append_list(llint)
+
+    print("TEST#{} List #1:".format(tno))
+    ll1.print()
+
+    print("TEST#{} List #2:".format(tno))
+    ll2.print()
+
+    inter = intersection(ll1, ll2)
+
+    print("TEST#{} intersection = {}".format(tno, inter.intersect()))
+    print("------------------------------------------------------------")
+
+    tno += 1
+    debug = False
+    l1 = [5, 6, 7, 8]
+    l2 = [15, 16, 17, 18]
+    lint = [9, 10, 11, 12, 13, 14]
+
+    ll1 = linkedList(l1, debug)
+    ll2 = linkedList(l2, debug)
+    llint = linkedList(lint, debug)
+
+    ll1.append_list(llint)
+    ll2.append_list(llint)
+
+    print("TEST#{} List #1:".format(tno))
+    ll1.print()
+
+    print("TEST#{} List #2:".format(tno))
+    ll2.print()
+
+    inter = intersection(ll1, ll2)
+
+    print("TEST#{} intersection = {}".format(tno, inter.intersect()))
+    print("------------------------------------------------------------")
+
+    tno += 1
+    debug = False
+    l1 = [1, 2, 3, 4, 5, 6, 7, 8]
+    l2 = [15, 14, 13, 12]
+    lint = []
+
+    ll1 = linkedList(l1, debug)
+    ll2 = linkedList(l2, debug)
+    llint = linkedList(lint, debug)
+
+    ll1.append_list(llint)
+    ll2.append_list(llint)
+
+    print("TEST#{} List #1:".format(tno))
+    ll1.print()
+
+    print("TEST#{} List #2:".format(tno))
+    ll2.print()
+
+    inter = intersection(ll1, ll2)
+
+    print("TEST#{} intersection = {}".format(tno, inter.intersect()))
+    print("------------------------------------------------------------")
+