이진 트리의 왼쪽 보기

Left view of following tree is 1 2 4 8.

          1
       /     \
     2        3
   /     \    /    \
  4     5   6       7
   \
     8

/* A Binary Tree node
class Node
{
    int data;
    Node left, right;

    Node(int item)
    {
        data = item;
        left = right = null;
    }
}*/
class Tree
{
    //Function to return list containing elements of left view of binary tree.
    int max = Integer.MIN_VALUE;
    ArrayList<Integer> leftView(Node root)
    {
      // Your code here
      ArrayList<Integer> list = new ArrayList<>();
      leftViewU(root,list,0);
      return list;
    }
        public void leftViewU(Node node,List<Integer> list,int current){
        if(node == null) return;
        if(current>max){
            list.add(node.data);
            max = current;
        }
        leftViewU(node.left,list,current+1); 
        leftViewU(node.right,list,current+1);
    }
}