103. Binary Tree Zigzag Level Order Traversal (java)

Author: bluesword12350

solution/0103.Binary Tree Zigzag Level Order Traversal/Solution.java

@@ -0,0 +1,21 @@
+class Solution {
+    private List<List<Integer>> list;
+    public List<List<Integer>> zigzagLevelOrder(TreeNode root) {
+        list = new ArrayList<>();
+        lever(root, 0);
+        for (int i = 1; i < list.size(); i = i + 2) {
+            List<Integer> nList = list.get(i);
+            List<Integer> nnl = new ArrayList<>();
+            for (int j = nList.size() - 1; j >= 0; j--) nnl.add(nList.get(j));
+            list.set(i, nnl);
+        }
+        return list;
+    }
+    private void lever(TreeNode root, int l) {
+        if (root == null) return;
+        while (l > list.size() - 1) list.add(new ArrayList<>());
+        list.get(l++).add(root.val);
+        lever(root.left, l);
+        lever(root.right, l);
+    }
+}