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Question
Formatted question description: https://leetcode.ca/all/100.html
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.
Example 1:
Input: p = [1,2,3], q = [1,2,3] Output: true
Example 2:
Input: p = [1,2], q = [1,null,2] Output: false
Example 3:
Input: p = [1,2,1], q = [1,1,2] Output: false
Constraints:
- The number of nodes in both trees is in the range
[0, 100]
. -104 <= Node.val <= 104
Algorithm
Depth first search DFS to recurse.
Code
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public class Same_Tree { /** * Definition for a binary tree node. * public class TreeNode { * int val; * TreeNode left; * TreeNode right; * TreeNode(int x) { val = x; } * } */ public class Solution_iteration { public boolean isSameTree(TreeNode p, TreeNode q) { if (p == null) { return q == null; } if (q == null) { return p == null; } Stack<TreeNode> sk1 = new Stack<TreeNode>(); Stack<TreeNode> sk2 = new Stack<TreeNode>(); sk1.push(p); sk2.push(q); while (!sk1.isEmpty() && !sk2.isEmpty()) { TreeNode current1 = sk1.pop(); TreeNode current2 = sk2.pop(); if (current1 == null && current2 == null) { continue; // @note: missed both null check } else if (current1 == null && current2 != null) { return false; } else if (current1 != null && current2 == null) { return false; } else if (current1.val != current2.val) { return false; } sk1.push(current1.left); sk2.push(current2.left); sk1.push(current1.right); sk2.push(current2.right); } // final check if (!sk1.isEmpty() || !sk2.isEmpty()) { return false; } return true; } } public class Solution_recursion { public boolean isSameTree(TreeNode p, TreeNode q) { if (p == null) { return q == null; } if (q == null) { return p == null; } if (p.val != q.val) { return false; } return isSameTree(p.left, q.left) && isSameTree(p.right, q.right); } } } ############ /** * Definition for a binary tree node. * public class TreeNode { * int val; * TreeNode left; * TreeNode right; * TreeNode() {} * TreeNode(int val) { this.val = val; } * TreeNode(int val, TreeNode left, TreeNode right) { * this.val = val; * this.left = left; * this.right = right; * } * } */ class Solution { public boolean isSameTree(TreeNode p, TreeNode q) { if (p == q) return true; if (p == null || q == null || p.val != q.val) return false; return isSameTree(p.left, q.left) && isSameTree(p.right, q.right); } }
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// OJ: https://leetcode.com/problems/same-tree/ // Time: O(N) // Space: O(H) class Solution { public: bool isSameTree(TreeNode* p, TreeNode* q) { return (!p && !q) || (p && q && p->val == q->val && isSameTree(p->left, q->left) && isSameTree(p->right, q->right)); } };
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# 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): def isSameTree(self, p, q): """ :type p: TreeNode :type q: TreeNode :rtype: bool """ if not p or not q: return p == q # covers: p=none and q!=none, q=none and p!=none, both none return p.val == q.val and self.isSameTree(p.left, q.left) and self.isSameTree(p.right, q.right) # iteration class Solution: def isSameTree(self, p: TreeNode, q: TreeNode) -> bool: if p is None: return q is None if q is None: return p is None stack1 = [p] stack2 = [q] while stack1 and stack2: current1 = stack1.pop() current2 = stack2.pop() if current1 is None and current2 is None: continue elif current1 is None or current2 is None: return False elif current1.val != current2.val: return False stack1.append(current1.left) stack2.append(current2.left) stack1.append(current1.right) stack2.append(current2.right) return not stack1 and not stack2
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/** * Definition for a binary tree node. * type TreeNode struct { * Val int * Left *TreeNode * Right *TreeNode * } */ func isSameTree(p *TreeNode, q *TreeNode) bool { if p == q { return true } if p == nil || q == nil || p.Val != q.Val { return false } return isSameTree(p.Left, q.Left) && isSameTree(p.Right, q.Right) }
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/** * Definition for a binary tree node. * class TreeNode { * val: number * left: TreeNode | null * right: TreeNode | null * constructor(val?: number, left?: TreeNode | null, right?: TreeNode | null) { * this.val = (val===undefined ? 0 : val) * this.left = (left===undefined ? null : left) * this.right = (right===undefined ? null : right) * } * } */ function isSameTree(p: TreeNode | null, q: TreeNode | null): boolean { if (p == null && q == null) { return true; } if (p == null || q == null || p.val !== q.val) { return false; } return isSameTree(p.left, q.left) && isSameTree(p.right, q.right); }
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/** * Definition for a binary tree node. * function TreeNode(val, left, right) { * this.val = (val===undefined ? 0 : val) * this.left = (left===undefined ? null : left) * this.right = (right===undefined ? null : right) * } */ /** * @param {TreeNode} p * @param {TreeNode} q * @return {boolean} */ var isSameTree = function (p, q) { if (!p && !q) return true; if (p && q) { return ( p.val === q.val && isSameTree(p.left, q.left) && isSameTree(p.right, q.right) ); } return false; };
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/** * Definition for a binary tree node. * class TreeNode { * public $val = null; * public $left = null; * public $right = null; * function __construct($val = 0, $left = null, $right = null) { * $this->val = $val; * $this->left = $left; * $this->right = $right; * } * } */ class Solution { /** * @param TreeNode $p * @param TreeNode $q * @return Boolean */ function isSameTree($p, $q) { if ($p == Null && $q == Null) { return true; } if ($p == Null || $q == Null) { return false; } if ($p->val != $q->val) { return false; } return $this->isSameTree($p->left, $q->left) && $this->isSameTree($p->right, $q->right); } }
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// Definition for a binary tree node. // #[derive(Debug, PartialEq, Eq)] // pub struct TreeNode { // pub val: i32, // pub left: Option<Rc<RefCell<TreeNode>>>, // pub right: Option<Rc<RefCell<TreeNode>>>, // } // // impl TreeNode { // #[inline] // pub fn new(val: i32) -> Self { // TreeNode { // val, // left: None, // right: None // } // } // } use std::rc::Rc; use std::cell::RefCell; impl Solution { fn dfs(p: &Option<Rc<RefCell<TreeNode>>>, q: &Option<Rc<RefCell<TreeNode>>>) -> bool { if p.is_none() && q.is_none() { return true; } if p.is_none() || q.is_none() { return false; } let r1 = p.as_ref().unwrap().borrow(); let r2 = q.as_ref().unwrap().borrow(); r1.val == r2.val && Self::dfs(&r1.left, &r2.left) && Self::dfs(&r1.right, &r2.right) } pub fn is_same_tree( p: Option<Rc<RefCell<TreeNode>>>, q: Option<Rc<RefCell<TreeNode>>>, ) -> bool { Self::dfs(&p, &q) } }