LeetCode

          Description:

                         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.

                         判断两棵树是不是相等。考虑null的情况。

          

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