Create TheRocket.md

Jerring · web-flow · commit f490296eb9c6 · 2018-12-04T17:05:13.000+08:00
diff --git a/2018.12.4-leetcode101/TheRocket.md b/2018.12.4-leetcode101/TheRocket.md
@@ -0,0 +1,63 @@
+```java
+// 递归
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode(int x) { val = x; }
+ * }
+ */
+class Solution {
+    public boolean isSymmetric(TreeNode root) {
+        return root == null || isSymmetric(root.left, root.right);
+    }
+
+    public boolean isSymmetric(TreeNode left, TreeNode right) {
+        if (left == null || right == null) {
+            return left == right;
+        }
+        return left.val == right.val && isSymmetric(left.left, right.right) && isSymmetric(left.right, right.left);
+    }
+}
+
+// 迭代
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode(int x) { val = x; }
+ * }
+ */
+class Solution {
+    public boolean isSymmetric(TreeNode root) {
+        if (root == null) {
+            return true;
+        }
+        LinkedList<TreeNode> stack = new LinkedList<>();
+        stack.push(root.left);
+        stack.push(root.right);
+        while (!stack.isEmpty()) {
+            TreeNode right = stack.poll();
+            TreeNode left = stack.poll();
+            if (left == null && right == null) {
+                continue;
+            }
+            if (left == null || right == null) {
+                return false;
+            }
+            if (left.val != right.val) {
+                return false;
+            }
+            stack.push(left.left);
+            stack.push(right.right);
+            stack.push(left.right);
+            stack.push(right.left);
+        }
+        return true;
+    }
+}
+```
