Question

919. Complete Binary Tree Inserter

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Description

A complete binary tree is a binary tree in which every level, except possibly the last, is completely filled, and all nodes are as far left as possible.

Design an algorithm to insert a new node to a complete binary tree keeping it complete after the insertion.

Implement the CBTInserter class:

• CBTInserter(TreeNode root) Initializes the data structure with the root of the complete binary tree.
• int insert(int v) Inserts a TreeNode into the tree with value Node.val == val so that the tree remains complete, and returns the value of the parent of the inserted TreeNode.
• TreeNode get_root() Returns the root node of the tree.

 

Example 1:

Input
["CBTInserter", "insert", "insert", "get_root"]
[[[1, 2]], [3], [4], []]
Output
[null, 1, 2, [1, 2, 3, 4]]

Explanation
CBTInserter cBTInserter = new CBTInserter([1, 2]);
cBTInserter.insert(3); // return 1
cBTInserter.insert(4); // return 2
cBTInserter.get_root(); // return [1, 2, 3, 4]

 

Constraints:

• The number of nodes in the tree will be in the range [1, 1000].
• 0 <= Node.val <= 5000
• root is a complete binary tree.
• 0 <= val <= 5000
• At most 104 calls will be made to insert and get_root.

Solutions

Solution 1

# Definition for a binary tree node.
# class TreeNode:
#   def __init__(self, val=0, left=None, right=None):
#     self.val = val
#     self.left = left
#     self.right = right
class CBTInserter:
  def __init__(self, root: TreeNode):
    self.tree = []
    q = deque([root])
    while q:
      for _ in range(len(q)):
        node = q.popleft()
        self.tree.append(node)
        if node.left:
          q.append(node.left)
        if node.right:
          q.append(node.right)

  def insert(self, val: int) -> int:
    pid = (len(self.tree) - 1) >> 1
    node = TreeNode(val)
    self.tree.append(node)
    p = self.tree[pid]
    if p.left is None:
      p.left = node
    else:
      p.right = node
    return p.val

  def get_root(self) -> TreeNode:
    return self.tree[0]


# Your CBTInserter object will be instantiated and called as such:
# obj = CBTInserter(root)
# param_1 = obj.insert(val)
# param_2 = obj.get_root()

/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *   int val;
 *   TreeNode left;
 *   TreeNode right;
 *   TreeNode() {}
 *   TreeNode(int val) { this.val = val; }
 *   TreeNode(int val, TreeNode left, TreeNode right) {
 *     this.val = val;
 *     this.left = left;
 *     this.right = right;
 *   }
 * }
 */
class CBTInserter {
  private List<TreeNode> tree;

  public CBTInserter(TreeNode root) {
    tree = new ArrayList<>();
    Deque<TreeNode> q = new ArrayDeque<>();
    q.offer(root);
    while (!q.isEmpty()) {
      TreeNode node = q.pollFirst();
      tree.add(node);
      if (node.left != null) {
        q.offer(node.left);
      }
      if (node.right != null) {
        q.offer(node.right);
      }
    }
  }

  public int insert(int val) {
    int pid = (tree.size() - 1) >> 1;
    TreeNode node = new TreeNode(val);
    tree.add(node);
    TreeNode p = tree.get(pid);
    if (p.left == null) {
      p.left = node;
    } else {
      p.right = node;
    }
    return p.val;
  }

  public TreeNode get_root() {
    return tree.get(0);
  }
}

/**
 * Your CBTInserter object will be instantiated and called as such:
 * CBTInserter obj = new CBTInserter(root);
 * int param_1 = obj.insert(val);
 * TreeNode param_2 = obj.get_root();
 */

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *   int val;
 *   TreeNode *left;
 *   TreeNode *right;
 *   TreeNode() : val(0), left(nullptr), right(nullptr) {}
 *   TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
 *   TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
 * };
 */
class CBTInserter {
public:
  vector<TreeNode*> tree;

  CBTInserter(TreeNode* root) {
    queue<TreeNode*> q{{root}};
    while (!q.empty()) {
      auto node = q.front();
      q.pop();
      tree.push_back(node);
      if (node->left) q.push(node->left);
      if (node->right) q.push(node->right);
    }
  }

  int insert(int val) {
    int pid = tree.size() - 1 >> 1;
    TreeNode* node = new TreeNode(val);
    tree.push_back(node);
    TreeNode* p = tree[pid];
    if (!p->left)
      p->left = node;
    else
      p->right = node;
    return p->val;
  }

  TreeNode* get_root() {
    return tree[0];
  }
};

/**
 * Your CBTInserter object will be instantiated and called as such:
 * CBTInserter* obj = new CBTInserter(root);
 * int param_1 = obj->insert(val);
 * TreeNode* param_2 = obj->get_root();
 */

/**
 * Definition for a binary tree node.
 * type TreeNode struct {
 *   Val int
 *   Left *TreeNode
 *   Right *TreeNode
 * }
 */
type CBTInserter struct {
  tree []*TreeNode
}

func Constructor(root *TreeNode) CBTInserter {
  q := []*TreeNode{root}
  tree := []*TreeNode{}
  for len(q) > 0 {
    node := q[0]
    tree = append(tree, node)
    q = q[1:]
    if node.Left != nil {
      q = append(q, node.Left)
    }
    if node.Right != nil {
      q = append(q, node.Right)
    }
  }
  return CBTInserter{tree}
}

func (this *CBTInserter) Insert(val int) int {
  pid := (len(this.tree) - 1) >> 1
  node := &TreeNode{Val: val}
  this.tree = append(this.tree, node)
  p := this.tree[pid]
  if p.Left == nil {
    p.Left = node
  } else {
    p.Right = node
  }
  return p.Val
}

func (this *CBTInserter) Get_root() *TreeNode {
  return this.tree[0]
}

/**
 * Your CBTInserter object will be instantiated and called as such:
 * obj := Constructor(root);
 * param_1 := obj.Insert(val);
 * param_2 := obj.Get_root();
 */

/**
 * Definition for a binary tree node.
 * class TreeNode {
 *   val: number
 *   left: TreeNode | null
 *   right: TreeNode | null
 *   constructor(val?: number, left?: TreeNode | null, right?: TreeNode | null) {
 *     this.val = (val===undefined ? 0 : val)
 *     this.left = (left===undefined ? null : left)
 *     this.right = (right===undefined ? null : right)
 *   }
 * }
 */

class CBTInserter {
  private root: TreeNode;
  private queue: TreeNode[];

  constructor(root: TreeNode | null) {
    this.root = root;
    this.queue = [this.root];
    while (true) {
      if (this.queue[0].left == null) {
        break;
      }
      this.queue.push(this.queue[0].left);
      if (this.queue[0].right == null) {
        break;
      }
      this.queue.push(this.queue[0].right);
      this.queue.shift();
    }
  }

  insert(val: number): number {
    if (this.queue[0].left != null && this.queue[0].right != null) {
      this.queue.shift();
    }
    const newNode = new TreeNode(val);
    this.queue.push(newNode);
    if (this.queue[0].left == null) {
      this.queue[0].left = newNode;
      return this.queue[0].val;
    }
    if (this.queue[0].right == null) {
      this.queue[0].right = newNode;
      return this.queue[0].val;
    }
    return 0;
  }

  get_root(): TreeNode | null {
    return this.root;
  }
}

/**
 * Your CBTInserter object will be instantiated and called as such:
 * var obj = new CBTInserter(root)
 * var param_1 = obj.insert(val)
 * var param_2 = obj.get_root()
 */

/**
 * Definition for a binary tree node.
 * function TreeNode(val, left, right) {
 *   this.val = (val===undefined ? 0 : val)
 *   this.left = (left===undefined ? null : left)
 *   this.right = (right===undefined ? null : right)
 * }
 */
/**
 * @param {TreeNode} root
 */
var CBTInserter = function (root) {
  this.tree = [];
  const q = [root];
  while (q.length) {
    const node = q.shift();
    this.tree.push(node);
    if (node.left) {
      q.push(node.left);
    }
    if (node.right) {
      q.push(node.right);
    }
  }
};

/**
 * @param {number} val
 * @return {number}
 */
CBTInserter.prototype.insert = function (val) {
  const pid = (this.tree.length - 1) >> 1;
  const node = new TreeNode(val);
  this.tree.push(node);
  const p = this.tree[pid];
  if (!p.left) {
    p.left = node;
  } else {
    p.right = node;
  }
  return p.val;
};

/**
 * @return {TreeNode}
 */
CBTInserter.prototype.get_root = function () {
  return this.tree[0];
};

/**
 * Your CBTInserter object will be instantiated and called as such:
 * var obj = new CBTInserter(root)
 * var param_1 = obj.insert(val)
 * var param_2 = obj.get_root()
 */