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.

还是用dfs。递归调用两个二叉树，并对比。类似Symmetric Tree 这道题。

三行即可。

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