<span style="font-size:18px;"><span style="font-size:18px;">/**LeetCode Symmetric Tree 對稱的樹
 * 思路：判斷一棵樹是否對稱，1.有左子樹就要有右子樹
 * 						2.除根節點外對稱節點值要相同
 * 注意：對稱後就是左子樹的左節點和右子樹的右節點比較
	 * Definition for binary tree
	 * public class TreeNode {
	 *     int val;
	 *     TreeNode left;
	 *     TreeNode right;
	 *     TreeNode(int x) { val = x; }
	 * }
	 */
package javaTrain;

public class Train8 { 
	    public boolean isSymmetric(TreeNode root) { 
	    	if(root == null) return true;
	    	if(root.left == null && root.right == null) return true;
	    	else if(root.left == null || root.right == null) return false;
	    	return help(root.left,root.right);
	    }
	    private boolean help(TreeNode left,TreeNode right){
	    	if(left == null && right == null) return true;
	    	else if(left == null || right == null) return false;
	    	if(left.val == right.val)
	    		return help(left.left,right.right ) && help(left.right,right.left);
	    	else return false;
	    }
}
</span></span>