116. Populating Next Right Pointers in Each Node

https://leetcode.com/problems/populating-next-right-pointers-in-each-node

Python

class Solution:
    def connect(self, root):
        if root is None:
            return root
        self._connect(root.left, root.right)
        return root

    def _connect(self, node1, node2):
        if node1 is None or node2 is None:
            return None
        node1.next = node2
        self._connect(node1.left, node1.right)
        self._connect(node2.left, node2.right)
        self._connect(node1.right, node2.left)

Go

func connect(root *Node) *Node {
    if root == nil {
        return nil
    }

    connectTwo(root.Left, root.Right)
    return root
}

func connectTwo(left *Node, right *Node) *Node {
    if left == nil || right == nil {
        return nil
    }

    left.Next = right
    connectTwo(left.Left, left.Right)
    connectTwo(right.Left, right.Right)
    connectTwo(left.Right, right.Left)
    return nil
}

Javascript

  const queue = [];
  if (root) queue.push(root);

  while (queue.length) {
    const total = queue.length;
    for (let i = 0; i < total; i++) {
      const node = queue.shift();
      if (i < total - 1) node.next = queue[0];

      if (node.left) queue.push(node.left);
      if (node.right) queue.push(node.right);
    }

  }
  return root;