Topics are as follows:
Given a binary tree
root
and a linked list withhead
as the first node.Return True if all the elements in the linked list starting from the
head
correspond to some downward path connected in the binary tree otherwise return False.In this context downward path means a path that starts at some node and goes downwards.
Example 1:
Input: head = [4,2,8], root = [1,4,4,null,2,2,null,1,null,6,8,null,null,null,null,1,3] Output: true Explanation: Nodes in blue form a subpath in the binary Tree.Example 2:
Input: head = [1,4,2,6], root = [1,4,4,null,2,2,null,1,null,6,8,null,null,null,null,1,3] Output: trueExample 3:
Input: head = [1,4,2,6,8], root = [1,4,4,null,2,2,null,1,null,6,8,null,null,null,null,1,3] Output: false Explanation: There is no path in the binary tree that contains all the elements of the linked list fromhead
.Constraints:
1 <= node.val <= 100
for each node in the linked list and binary tree.- The given linked list will contain between
1
and100
nodes.- The given binary tree will contain between
1
and2500
nodes.
Outline of Solution : sequentially determining whether each node in the tree can be used as the first node to the list.
code show as below:
# 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 class Solution(object): res = False def compare(self,tree_node,list_node): if self.res == True: return elif list_node.next == None and list_node.val == tree_node.val: self.res = True return elif list_node.val != tree_node.val: return elif list_node.next == None: return if tree_node.left != None: self.compare(tree_node.left,list_node.next) if tree_node.right != None: self.compare(tree_node.right,list_node.next) def isSubPath(self, head, root): """ :type head: ListNode :type root: TreeNode :rtype: bool """ self.res = False def recursive(tree_node): self.compare(tree_node,head) if self.res == True: return if tree_node.left != None: recursive(tree_node.left) if tree_node.right != None: recursive(tree_node.right) recursive(root) return self.res