Merge pull request #3427 from adhamahmad/binary-tree-zigzag-level-order-traversal

Create 0103-binary-tree-zigzag-level-order-traversal.java

Author: felivalencia3

Diff for: java/0103-binary-tree-zigzag-level-order-traversal.java

@@ -0,0 +1,30 @@
+class Solution {
+    boolean reverse = false; // flag to detrmine the direction left or right
+    List<List<Integer>> sol = new ArrayList<List<Integer>>();
+    public List<List<Integer>> zigzagLevelOrder(TreeNode root) {
+        if(root == null){return sol;}
+        Queue<TreeNode> queue = new LinkedList<>();
+        queue.add(root);
+        while( !queue.isEmpty()){  
+            List<Integer> temp = new ArrayList<Integer>();
+            int size =queue.size();
+            for(int i=0; i < size; i++){
+                TreeNode node = queue.poll();
+                temp.add(node.val);
+                if(node.left != null){
+                    queue.add(node.left);
+                }
+                if(node.right != null){
+                    queue.add(node.right);
+                }
+            }
+            if(reverse){
+                Collections.reverse(temp);
+            }
+            reverse = !reverse;
+            sol.add(temp);
+        }
+        return sol;
+    }
+
+}