BinaryTreeVerticalOrder

Java/BinaryTreeVerticalOrder.java

@@ -0,0 +1,84 @@
+import java.util.*;
+
+class TreeNode {
+    int val;
+    TreeNode left;
+    TreeNode right;
+
+    TreeNode(int val) {
+        this.val = val;
+        left = null;
+        right = null;
+    }
+}
+
+public class BinaryTreeVerticalOrder {
+    class NodeColumnPair {
+        TreeNode node;
+        int column;
+
+        NodeColumnPair(TreeNode node, int column) {
+            this.node = node;
+            this.column = column;
+        }
+    }
+
+    public List<List<Integer>> verticalOrder(TreeNode root) {
+        List<List<Integer>> result = new ArrayList<>();
+        if (root == null) {
+            return result;
+        }
+
+        Map<Integer, List<Integer>> columnMap = new HashMap<>();
+        Queue<NodeColumnPair> queue = new LinkedList<>();
+        int minColumn = 0, maxColumn = 0;
+        queue.offer(new NodeColumnPair(root, 0));
+
+        while (!queue.isEmpty()) {
+            NodeColumnPair pair = queue.poll();
+            TreeNode node = pair.node;
+            int column = pair.column;
+
+            columnMap.putIfAbsent(column, new ArrayList<>());
+            columnMap.get(column).add(node.val);
+
+            minColumn = Math.min(minColumn, column);
+            maxColumn = Math.max(maxColumn, column);
+
+
+            if (node.left != null) {
+                queue.offer(new NodeColumnPair(node.left, column - 1));
+            }
+
+            if (node.right != null) {
+                queue.offer(new NodeColumnPair(node.right, column + 1));
+            }
+        }
+
+
+        for (int i = minColumn; i <= maxColumn; i++) {
+            result.add(columnMap.get(i));
+        }
+
+        return result;
+    }
+
+    public static void main(String[] args) {
+        BinaryTreeVerticalOrder solution = new BinaryTreeVerticalOrder();
+
+
+        TreeNode root = new TreeNode(3);
+        root.left = new TreeNode(9);
+        root.right = new TreeNode(20);
+        root.right.left = new TreeNode(15);
+        root.right.right = new TreeNode(7);
+
+
+        List<List<Integer>> verticalOrderTraversal = solution.verticalOrder(root);
+
+
+        for (List<Integer> column : verticalOrderTraversal) {
+            System.out.println(column);
+        }
+    }
+}