Same Tree

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.

很简单的，遍历一次就可以知道是否是相等树了，可以变成迭代法，效率会快点。

和Symmetric Tree基本是一样的。

/**
 * Definition for binary tree
 * 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){
            if(!isSameTree(p.left,q.left)){
                return false;
            }
            if(!isSameTree(p.right,q.right)){
                return false;
            }
            return true;
        }else{
            return false;
        }
    }
}