【LeetCode OJ】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.

/**
 * 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) {
        return preOrder(p, q);
    }
    public boolean preOrder(TreeNode p, TreeNode q) {
		if (p == null && q == null)
			return true;
		if((p == null && q != null) || (q == null && p != null))
			return false;
		if(!preOrder(p.left, q.left)){
			return false;
		}
		if(!preOrder(p.right, q.right)){
			return false;
		}
		if (p.val != q.val)
			return false;
		return true;
	}
}