Create linked-list-in-binary-tree.py

Author: kamyu104

Python/linked-list-in-binary-tree.py

@@ -0,0 +1,84 @@
+# Time:  O(n + l)
+# Space: O(h + l)
+
+# Definition for singly-linked list.
+class ListNode(object):
+    def __init__(self, x):
+        self.val = x
+        self.next = None
+
+
+# Definition for a binary tree node.
+class TreeNode(object):
+    def __init__(self, x):
+        self.val = x
+        self.left = None
+        self.right = None
+
+
+# kmp solution
+class Solution(object):
+    def isSubPath(self, head, root):
+        """
+        :type head: ListNode
+        :type root: TreeNode
+        :rtype: bool
+        """
+        def getPrefix(head):
+            pattern, prefix = [head.val], [-1]
+            j = -1
+            node = head.next
+            while node:
+                while j+1 and pattern[j+1] != node.val:
+                    j = prefix[j]
+                if pattern[j+1] == node.val:
+                    j += 1
+                pattern.append(node.val)
+                prefix.append(j)
+                node = node.next
+            return pattern, prefix
+            
+        def dfs(pattern, prefix, root, j):
+            if not root:
+                return False
+            while j+1 and pattern[j+1] != root.val:
+                j = prefix[j]
+            if pattern[j+1] == root.val:
+                j += 1
+            if j+1 == len(pattern):
+                return True
+            return dfs(pattern, prefix, root.left, j) or \
+                   dfs(pattern, prefix, root.right, j)
+        
+        if not head:
+            return True
+        pattern, prefix = getPrefix(head)
+        return dfs(pattern, prefix, root, -1)
+    
+
+# Time:  O(n * min(h, l))
+# Space: O(h)
+# dfs solution
+class Solution2(object):
+    def isSubPath(self, head, root):
+        """
+        :type head: ListNode
+        :type root: TreeNode
+        :rtype: bool
+        """
+        def dfs(head, root):
+            if not head:
+                return True
+            if not root:
+                return False
+            return root.val == head.val and \
+                   (dfs(head.next, root.left) or 
+                    dfs(head.next, root.right))
+    
+        if not head:
+            return True
+        if not root:
+            return False
+        return dfs(head, root) or \
+               self.isSubPath(head, root.left) or \
+               self.isSubPath(head, root.right)