LeetCode 100. Same Tree 等价二叉树

Description

https://leetcode.com/problems/same-tree/description/

Given two binary trees, 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:     1         1
          / \       / \
         2   3     2   3

        [1,2,3],   [1,2,3]

Output: true

Example 2:

Input:     1         1
          /           \
         2             2

        [1,2],     [1,null,2]

Output: false

Example 3:

Input:     1         1
          / \       / \
         2   1     1   2

        [1,2,1],   [1,1,2]

Output: false

Explanation

此题的目标是要实现 isSameTree(TreeNode p, TreeNode q) 函数。

有两种情况会使 isSameTree(TreeNode p, TreeNode q) 返回true:

  1. 当p和q都为null时候
  2. 当p和q都不为null, p和q的值相等,并且p和q的左右子树都相同

Video Tutorial

Java Solution

/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
class Solution {
    public boolean isSameTree(TreeNode p, TreeNode q) {
        if (p == null && q == null) {
            return true;
        }
        
        if (p != null && q != null) {
            if (p.val == q.val && isSameTree(p.left, q.left) && isSameTree(p.right, q.right)) {
                return true;
            }            
        }
        
        return false;
    }
}

发表评论

电子邮件地址不会被公开。 必填项已用*标注