【LeetCode_101】 對稱二叉樹

描述：

給定一個二叉樹，檢查它是否是鏡像對稱的。

示例：例如，二叉樹 [1,2,2,3,4,4,3] 是對稱的

代碼：

/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
class Solution {
    public boolean isSymmetric(TreeNode root) {
        if (root == null) return true;
        return campSymm(root.left, root.right);
    }
    private boolean campSymm(TreeNode nodeLeft, TreeNode nodeRight) {
        if (nodeLeft == null && nodeRight == null) return true;
        if (nodeLeft == null 
        || nodeRight == null 
        || nodeRight.val != nodeLeft.val) {
            return false;
        }
        return campSymm(nodeLeft.left, nodeRight.right)
            && campSymm(nodeLeft.right, nodeRight.left);    
    }      
}