leetcode 100. Same Tree

题目大意：

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