Leetcode Same Tree 判斷兩棵二叉樹是否相同

題目：

Given two binary trees, write a function to check if they are equal or not.

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

分析：

先判斷當前的兩個樹節點是否相同，如果不相同，直接返回false。如果相同，再遞歸的看左子樹和右子樹是否相同。

Java代碼實現：

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