Pretty Print a Binary Search Tree

prettyPrintTree.java

static class Wrapper {
  TreeNode node;
  int level;
  Wrapper(TreeNode node, int level) {
    this.node = node;
    this.level = level;
  }
}

static int skip;
public void pretty() {
  skip = 0;
  if(root == null) {
    System.out.println("Empty Tree!");
    return;
  }
  
  setPos(root); // Find line position for each node
  pretty(root); // level-order traversal display the nodes
}

public void setPos(TreeNode node) {
  if(node != null) {
    setPos(node.left);
    node.util = skip; // Store skip value in util data member
    skip += 2;        // Update for printing THIS node
    setPos(node.right);
  }
}

public void pretty(TreeNode) {
  Queue<Wrapper> que = new Queue<Wrapper>();
  int position = 0, // position in output line
      level = 1,    // level being processed
      current;      // value for node ABOUT to process
  que.offer(new Wrapper(node, level));
  
  while(!que.isEmpty()) {
    Wrapper item = queue.remove();
    node = item.node;
    current = item.level;
    if(node.left != null)
      queue.offer(new Wrapper(node.left, current+1));
    if(node.right != null)
      queue.offer(new Wrapper(node.right, current+1));
    if(current != level) {
      System.out.println();
    }
    for(; position < node.util; position++) {
      System.out.print(" ");
      System.out.print("%2", node.data);
      position += 2;
    }
    System.out.println(); // Final line termination
  }
}