[Vssue]0101.对称二叉树.md

[youngyangyang04]

https://www.programmercarl.com/0101.%E5%AF%B9%E7%A7%B0%E4%BA%8C%E5%8F%89%E6%A0%91.html

[Du1in9]

class Solution {
    public boolean isSymmetric(TreeNode root) {
        if (root == null) return true;
        return compare(root.left, root.right);
    }

    private boolean compare(TreeNode left, TreeNode right) {
        if(left == null && right == null){
            return true;
        } else if(left != null && right == null){
            return false;
        } else if(left == null && right != null){
            return false;
        } else if(left.val != right.val){
            return false;
        }
        boolean outside = compare(left.left, right.right);
        boolean inside = compare(left.right, right.left);               
        return outside && inside;
    }
}

[ZYKWLJ]

就简简单单的递归罢了：

class Solution {     public boolean isSymmetric(TreeNode root) {        if(root==null)return true;         return isMirror(root.left,root.right);     }

    private boolean isMirror(TreeNode left,TreeNode right){         if(left==null&&right==null)return true;         else if(left==null||right==null)return false;         return (left.val==right.val)&&isMirror(left.left,right.right)&&isMirror(left.right,right.left);     } }

[mockyd]

我怎么看到一个二叉树就想用层序遍历做。。