Leetcode :: Same Tree

Problem

Given the roots of two binary trees p and q, write a function to check if they are the same or not.

Two binary trees are considered the same if they are structurally identical, and the nodes have the same value.

Guess

• 두 트리의 모든 노드가 동일한지를 묻는 문제다.

• 비선형 자료구조기 때문에 단순 linear 탐색이 불가하다.

• dfs, bfs 모두 적용해보자.

Sol 1. DFS (Recursion)

# Definition for a binary tree node.
# class TreeNode:
#     def __init__(self, val=0, left=None, right=None):
#         self.val = val
#         self.left = left
#         self.right = right
class Solution:
    def isSameTree(self, p: TreeNode, q: TreeNode) -> bool:
        if not p and not q:
            return True
        if not p or not q:
            return False
        if p.val != q.val:
            return False
        
        return self.isSameTree(p.left, q.left) and self.isSameTree(p.right, q.right)

Sol 2. BFS (Queue)

from collections import deque

class Solution:
    def isSameNode(self, p,q):
        if not p and not q:
            return True
        if not p or not q:
            return False
        if p.val != q.val:
            return False
        
        return True
    
    
    def isSameTree(self, p: TreeNode, q: TreeNode) -> bool:
        dq = deque([(p, q)])
        
        while dq:
            p,q = dq.popleft()
            
            if not self.isSameNode(p,q):
                return False
            
            if p:
                dq.append((p.left, q.left))
                dq.append((p.right, q.right))
            
        return True