对称的二叉树

/**
 * 
 * @author gentleKay
 * 题目描述
 * 请实现一个函数，用来判断一颗二叉树是不是对称的。
 * 注意，如果一个二叉树同此二叉树的镜像是同样的，定义其为对称的。
 */

public class Main56 {

	public static void main(String[] args) {
		// TODO Auto-generated method stub
		TreeNode root = new TreeNode(1);
		root.left = new TreeNode(2);
		root.right = new TreeNode(2);
		
		root.left.left = new TreeNode(3);
		root.left.right = new TreeNode(4);
		
		root.right.left = new TreeNode(4);
		root.right.right = new TreeNode(3);
		
//		root.left.left.left = new TreeNode(5);
		
		System.out.println(Main56.isSymmetrical(root));
		
	}
	
	public static class TreeNode {
	    int val = 0;
	    TreeNode left = null;
	    TreeNode right = null;

	    public TreeNode(int val) {
	        this.val = val;

	    }
	}
	
    static boolean isSymmetrical(TreeNode pRoot){
    	if (pRoot == null) {
    		return true;
    	}
    	
    	return isSym(pRoot.left, pRoot.right);
    }
    
    static boolean isSym(TreeNode RootLeft, TreeNode RootRight) {
    	if (RootLeft == null && RootRight == null) {
    		return true;
    	}
    	if (RootLeft == null || RootRight == null) {
    		return false;
    	}
    	
    	if (RootLeft.val == RootRight.val) {
    		return isSym(RootLeft.left,RootRight.right) && isSym(RootLeft.right, RootRight.left);
    	}
    	return false;
    }
}