feat: 对称二叉树

Author: sl1673495

二叉树/对称二叉树-101.js

@@ -0,0 +1,28 @@
+/**
+ * Definition for a binary tree node.
+ * function TreeNode(val) {
+ *     this.val = val;
+ *     this.left = this.right = null;
+ * }
+ */
+/**
+ * @param {TreeNode} root
+ * @return {boolean}
+ */
+var isSymmetric = function (root) {
+  if (!root) return true
+  let helper = (left, right) => {
+    if (!left && !right) {
+      return true
+    }
+    if (!left || !right) {
+      return false
+    }
+    if (left.val === right.val) {
+      return helper(left.left, right.right) && helper(left.right, right.left)
+    } else {
+      return false
+    }
+  }
+  return helper(root, root)
+}