【LeetCode】Symmetric Tree 推断一棵树是否是镜像的

<span style="font-size:18px;"><span style="font-size:18px;">/**LeetCode Symmetric Tree 对称的树
* 思路：推断一棵树是否对称，1.有左子树就要有右子树
* 						2.除根节点外对称节点值要同样
* 注意：对称后就是左子树的左节点和右子树的右节点比較
* Definition for binary tree
* public class TreeNode {
*     int val;
*     TreeNode left;
*     TreeNode right;
*     TreeNode(int x) { val = x; }
* }
*/
package javaTrain;

public class Train8 {
public boolean isSymmetric(TreeNode root) {
if(root == null) return true;
if(root.left == null && root.right == null) return true;
else if(root.left == null || root.right == null) return false;
return help(root.left,root.right);
}
private boolean help(TreeNode left,TreeNode right){
if(left == null && right == null) return true;
else if(left == null || right == null) return false;
if(left.val == right.val)
return help(left.left,right.right ) && help(left.right,right.left);
else return false;
}
}
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