剑指offer-对称的二叉树

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

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

    }

}
*/
public class Solution {
    boolean isSymmetrical(TreeNode pRoot)
    {
        if(pRoot == null){
            return true;
        }
        return judge(pRoot.left,pRoot.right);
    }
    
    public boolean judge(TreeNode a,TreeNode b){
        //相同为true
        if(a == null && b == null){
            return true;
        }
        //只有一个为null，说明不对称
        if(a == null||b==null){
            return false;
        }
        //相同继续判断左右节点的对称性，不同则返回false
        if(a.val == b.val){
            return judge(a.left,b.right)&&judge(a.right,b.left);
        }else{
            return false;
        }
    }
}