题目

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思路

  • 对称二叉树也就是树的左右子树是对称的，也就是left.left 等于 right.right和left.right 等于 right.left

    代码

    1.   public boolean isSymmetric(TreeNode root) {
    2.       if (root == null) return true;
    3.       return recur(root.left, root.right);
    4.   }
    6.   public boolean recur(TreeNode left, TreeNode right) {
    7.       if (left != null && right != null && left.val == right.val)
    8.           return recur(left.right, right.left) && recur(left.left, right.right);
    9.       if (left == null && right == null) return true;
    10.       return false;
    11.   }

    对称二叉树