algorithm/[101]对称二叉树.java at master · Ada0910/algorithm

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//leetcode submit region begin(Prohibit modification and deletion)

/**

* Definition for a binary tree node.

* public class TreeNode {

* int val;

* TreeNode left;

* TreeNode right;

* TreeNode() {}

* TreeNode(int val) { this.val = val; }

* TreeNode(int val, TreeNode left, TreeNode right) {

* this.val = val;

* this.left = left;

* this.right = right;

* }

class Solution {

public boolean isSymmetric(TreeNode root) {

if (root == null) {

return true;

} else {

return dsf(root.left, root.right);

}

/**

* 终止的条件：

* （1）都为空

* (2)左右只有一个为空

* (3)左右的值不相等

private Boolean dsf(TreeNode left, TreeNode right) {

if (left == null && right == null) {

return true;

}

if (left == null || right == null) {

return false;

}

if (left.val != right.val) {

return false;

}

return dsf(left.left,right.right)&& dsf(left.right,right.left);

}

//leetcode submit region end(Prohibit modification and deletion)