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public class Main { | |
public static Map<Integer, Integer> ht = new HashMap<>();; | |
public static void topView(Node root, int level) { | |
if (root == null) | |
return; | |
Queue<QueuePack> queue = new LinkedList<>(); | |
queue.add(new QueuePack(level, root)); | |
while (!queue.isEmpty()) { | |
QueuePack q = queue.remove(); | |
Node tnode = q.tnode; | |
int lvl = q.level; | |
// check if this is the first node you are visiting at the level | |
if (!ht.containsKey(lvl)) { | |
// print it, its the first element at his level | |
System.out.print(tnode.data + " "); | |
ht.put(lvl, tnode.data); | |
} | |
// add the left and right children of visiting nodes to the queue | |
if (tnode.left != null) { | |
queue.add(new QueuePack(lvl - 1, tnode.left)); | |
} | |
if (tnode.right != null) { | |
queue.add(new QueuePack(lvl + 1, tnode.right)); | |
} | |
} | |
} | |
public static void main(String args[]) { | |
Node root = new Node(1); | |
root.left = new Node(2); | |
root.right = new Node(3); | |
root.left.left = new Node(4); | |
root.left.left.left = new Node(8); | |
root.left.left.right = new Node(9); | |
root.left.right = new Node(5); | |
root.right.left = new Node(6); | |
root.right.right = new Node(7); | |
topView(root, 0); | |
} | |
} | |
class Node { | |
int data; | |
Node left; | |
Node right; | |
public Node(int data) { | |
this.data = data; | |
left = null; | |
right = null; | |
} | |
} | |
// this class' represents the items stored in queue | |
class QueuePack { | |
int level; | |
Node tnode; | |
public QueuePack(int level, Node tnode) { | |
this.level = level; | |
this.tnode = tnode; | |
} | |
} |
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