二叉树对称

package Struct;

public class TreeNode {
    public int val = 0;
    public TreeNode left = null;
    public TreeNode right = null;

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

    @Override
    public String toString() {
        return "TreeNode [val=" + val + ", left=" + left + ", right=" + right + "]";
    }
}

package offer;

import Struct.TreeNode;
/**
 * 
 * 二叉树的镜像定义：源二叉树 
            8
           /  
          6   10
         /   / 
        5  7 9  11
        
   5 6 7 8 9 10 11
        镜像二叉树
            8
           /  
          10   6
         /   / 
        11 9 7   5
   11 10 9 8 7 6 5    
 * @author 爱不会绝迹
 *
 *
 *    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 Problem38 {

    public static boolean isSymmetrical(TreeNode pRoot) {
        if(pRoot==null){
            return true;
        }
        return isMirror(pRoot.left,pRoot.right);
    }
    
    public static boolean isMirror(TreeNode left,TreeNode right){
        if(left==null&&right==null){
            return true;
        }
        if(left==null || right==null){
            return false;
        }
        return left.val==right.val&&isMirror(left.left,right.right)&&isMirror(left.right,right.left);
    }
    
    private static int index = -1;
    public static void main(String[] args) {
        Integer[] array = {5,3,3,4,null,null,4,2,null,null,2,1,null,null,1};
        TreeNode tree = createBinTree(array);
        boolean b = isSymmetrical(tree);
        System.out.println(b);
    }
    private static TreeNode createBinTree(Integer[] array) {
        TreeNode tree = null;
        if(index < array.length-1 && array[++index]!=null){
            tree = new TreeNode(array[index]);
            tree.left = createBinTree(array);
            tree.right = createBinTree(array);
        }
        return tree;
    }
}