From 14b236eb84eb903be670ecad2fe9b36e0c8dad8c Mon Sep 17 00:00:00 2001
From: "Bradley M. Small" <bradley_small@hotmail.com>
Date: Wed, 16 Oct 2019 17:15:19 -0400
Subject: [PATCH] fixing broken solution and adding 2 more
---
.tags | 15 ++++++++++
main.py | 90 +++++++++++++++++++++++++++++++++------------------------
2 files changed, 67 insertions(+), 38 deletions(-)
create mode 100644 .tags
diff --git a/.tags b/.tags
new file mode 100644
index 0000000..1f6c81b
--- /dev/null
+++ b/.tags
@@ -0,0 +1,15 @@
+!_TAG_FILE_FORMAT 2 /extended format; --format=1 will not append ;" to lines/
+!_TAG_FILE_SORTED 1 /0=unsorted, 1=sorted, 2=foldcase/
+!_TAG_PROGRAM_AUTHOR Darren Hiebert /dhiebert@users.sourceforge.net/
+!_TAG_PROGRAM_NAME Exuberant Ctags //
+!_TAG_PROGRAM_URL http://ctags.sourceforge.net /official site/
+!_TAG_PROGRAM_VERSION 5.9~svn20110310 //
+LList main.py /^class LList:$/;" c
+Node main.py /^class Node:$/;" c
+__init__ main.py /^ def __init__(self, head):$/;" m class:LList
+__init__ main.py /^ def __init__(self, val, next=None):$/;" m class:Node
+main main.py /^def main():$/;" f
+next main.py /^ def next(self):$/;" m class:LList
+reverse main.py /^ def reverse(self):$/;" m class:LList
+rewind main.py /^ def rewind(self):$/;" m class:LList
+show main.py /^ def show(self):$/;" m class:LList
diff --git a/main.py b/main.py
index 22a777c..24deec5 100755
--- a/main.py
+++ b/main.py
@@ -7,7 +7,7 @@ some exception handling and proper error checking. """
class Node:
""" The node will be the basis of a singly linked list """
def __init__(self, val, next=None):
- self.val = val;
+ self.val = str(val);
self.next = next
@@ -33,7 +33,7 @@ class LList:
print("[", end = '')
comma = ''
while n:
- print(comma, n.val, end = '')
+ print(comma, n.val if n.val[0] != '~' else n.val[1:], end = '')
comma = ','
n = n.next
print(" ]")
@@ -54,45 +54,14 @@ class LList:
def main():
""" Main driver create lists, reverse them, find beginning overlap """
# This is just setup
- mlist = LList(Node(3,Node(7,Node(8,Node(10)))))
- nlist = LList(Node(99,Node(1,Node(8,Node(10)))))
+ cnode = Node(8,Node(10))
+ mlist = LList(Node(3,Node(7,cnode)))
+ nlist = LList(Node(99,Node(1,cnode)))
mlist.show()
nlist.show()
-
-
-
- # list reversal in place solution
- # this is in constant space but the solution is actually
- # in O(m+n+l) where l is the final length of the overlapped
- # string. Still in constant space since the reversal is in place
- nlist.reverse()
- mlist.reverse()
-
- # constant space
- # O(m+n) time
- nnode = nlist.rewind()
- mnode = mlist.rewind()
-
- overlap = None
- while nnode.val == mnode.val:
- overlap = nnode
- nnode = nlist.next()
- mnode = mlist.next()
-
- print("The overlap = ", overlap.val)
-
- # At this point the list would have to be reversed again to actually
- # get the true overlapped list, though not part of the problem it
- # doubles the effort to achieve
- nlist.reverse()
- mlist.reverse()
-
- print("The overlap list : ", end ='')
- LList(overlap).show()
-
# solution using 2 "pointers" solves the O(m+n) in constant space
# aspect of the problem.
mwalker = mlist.head
@@ -107,11 +76,56 @@ def main():
nwalker = mlist.heead
print("The overlap = ", nwalker.val);
- # Getting the actual list, though not part of the problem no longer
- # takes double the processing.
+ # Getting the actual list, though not part of the problem
+ # is pretty much free
print("The overlap list is:", end ='')
LList(nwalker).show();
+ # this solution is partially destructive in that it
+ # modifies the val. For this I changed it to a string
+ # and added a ~ to ones visited in one list. when traversing
+ # the other list finding the ~ shows the overlap. The show()
+ # was modified to not show the ~. Certainly a cleanup could be
+ # employed to go through an remove all the ~.
+ # This is also O(n+m)
+ mnode = mlist.rewind()
+ while mnode:
+ mnode.val = "~" + str(mnode.val)
+ mnode = mnode.next
+
+ nnode = nlist.rewind()
+ while nnode.val[0] != '~':
+ nnode = nlist.next()
+ overlap = nnode
+ print("The overlap = ", overlap.val[1:])
+ print("The overlap list : ", end ='')
+ LList(overlap).show()
+
+
+
+ # this solution is destructive as it sets
+ # all the "next" pointers to None so once the
+ # overlap is found you are done, but you no longer
+ # have the rest of the list
+ mnode = mlist.rewind()
+ while mnode:
+ temp = mnode.next
+ mnode.next = None
+ mnode = temp
+
+ # constant space
+ # O(m+n) time
+ nnode = nlist.rewind()
+
+ overlap = None
+ while nnode.next:
+ nnode = nlist.next()
+ overlap = nnode
+
+ print("The overlap = ", overlap.val[1:])
+ print("The overlap list : ", end ='')
+ LList(overlap).show()
+
if __name__ == "__main__":
main()
--
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