LeetCode-Same Tree

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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

题意：判断两颗给定的二叉树是否相同，要求节点的值也要相同；

解法：我们可以利用递归的思想，依次判断两颗树的当前节点是否相同，之后再判断其左节点和右节点；

Java

/**
 * 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) {
            return q == null ? true : false;
        } else if (q == null) {
            return false;
        }
        if (p.val != q.val) return false;
        return isSameTree(p.left, q.left) && isSameTree(p.right, q.right);
    }
}

Scala

/**
 * Definition for a binary tree node.
 * class TreeNode(var _value: Int) {
 *   var value: Int = _value
 *   var left: TreeNode = null
 *   var right: TreeNode = null
 * }
 */
object Solution {
    def isSameTree(p: TreeNode, q: TreeNode): Boolean = {
        if (p == null && q == null) return true
        if (p == null || q == null) return false
        p.value == q.value && isSameTree(p.left, q.left) && isSameTree(p.right, q.right)
    }
}