diff --git a/src/main/java/contest/y2022/m9/Week311.java b/src/main/java/contest/y2022/m9/Week311.java
new file mode 100644
index 0000000..46d1342
--- /dev/null
+++ b/src/main/java/contest/y2022/m9/Week311.java
@@ -0,0 +1,118 @@
+package contest.y2022.m9;
+
+import com.code.leet.entiy.TreeNode;
+
+import java.util.*;
+
+public class Week311 {
+    public static void main(String[] args) {
+        Week311 soluytion = new Week311();
+        //TreeNode root = new TreeNode(Arrays.asList(2, 3, 5, 8, 13, 21, 34));
+        TreeNode root = new TreeNode(Arrays.asList(0, 1, 2, 0, 0, 0, 0, 1, 1, 1, 1, 2, 2, 2, 2));
+        soluytion.reverseOddLevels(root);
+    }
+
+    class Trie {
+        private Trie[] children;
+        private int cnt;
+
+        public Trie() {
+            children = new Trie[26];
+            cnt = 0;
+        }
+
+        public void insert(String word) {
+            Trie node = this;
+            for (int i = 0; i < word.length(); i++) {
+                char ch = word.charAt(i);
+                int index = ch - 'a';
+                if (node.children[index] == null) {
+                    node.children[index] = new Trie();
+                }
+                node = node.children[index];
+                node.cnt += 1;
+            }
+        }
+
+        private int search(String prefix) {
+            Trie node = this;
+            int cnt = 0;
+            for (int i = 0; i < prefix.length(); i++) {
+                char ch = prefix.charAt(i);
+                int index = ch - 'a';
+                if (node.children[index] == null) {
+                    break;
+                }
+                node = node.children[index];
+                cnt += node.cnt;
+            }
+            return cnt;
+        }
+    }
+
+    public int[] sumPrefixScores(String[] words) {
+        Trie trie = new Trie();
+        for (String word : words) {
+            trie.insert(word);
+        }
+        int[] arrs = new int[words.length];
+        for (int i = 0; i < words.length; i++) {
+            arrs[i] = trie.search(words[i]);
+        }
+        return arrs;
+    }
+
+    public TreeNode reverseOddLevels(TreeNode root) {
+        List<Integer> list = new ArrayList<>();
+        Queue<TreeNode> queue = new LinkedList<>();
+        queue.add(root);
+        while (!queue.isEmpty()) {
+            TreeNode node = queue.poll();
+            list.add(node.val);
+            if (node.left != null) {
+                queue.add(node.left);
+                queue.add(node.right);
+            }
+        }
+        root = new TreeNode(list.get(0));
+        queue.add(root);
+        int n = 1;
+        int min = 0;
+        int max = 0;
+        int cnt = 1;
+        int mul = 1;
+        while (cnt < list.size()) {
+            min = max + 1;
+            max += mul * 2;
+            cnt += mul * 2;
+            if (n % 2 == 0) {
+                for (int i = min; i <= max; i = i + 2) {
+                    TreeNode node = queue.poll();
+                    TreeNode left = new TreeNode(list.get(i));
+                    TreeNode right = new TreeNode(list.get(i + 1));
+                    node.left = left;
+                    node.right = right;
+                    queue.add(left);
+                    queue.add(right);
+                }
+            } else {
+                for (int i = max; i >= min; i = i - 2) {
+                    TreeNode node = queue.poll();
+                    TreeNode left = new TreeNode(list.get(i));
+                    TreeNode right = new TreeNode(list.get(i - 1));
+                    node.left = left;
+                    node.right = right;
+                    queue.add(left);
+                    queue.add(right);
+                }
+            }
+            n++;
+            mul *= 2;
+        }
+        return root;
+    }
+
+    public int smallestEvenMultiple(int n) {
+        return n % 2 == 0 ? n : n * 2;
+    }
+}