623. Add One Row to Tree

AddOneRow.cs

public class Solution {
  public TreeNode AddOneRow(TreeNode root, int val, int depth) {
    if(depth == 1){
      var tempLeft = root;
      root = new TreeNode(val);
      root.left = tempLeft;
      return root;
    }

    var queue = new Queue<TreeNode>();
    queue.Enqueue(root);
    var currentDepth = 1;
    
    while(queue.Count > 0 && currentDepth < depth){
      var sz = queue.Count;
      
      while(sz > 0){
        var current = queue.Dequeue();
        sz--;
        if(currentDepth == depth - 1){
          var tempLeft = current.left;
          var tempRight = current.right;
          current.left = new TreeNode(val);
          current.right = new TreeNode(val);

          current.left.left = tempLeft;
          current.right.right = tempRight;
          continue;
        }

        if(current.left is not null) 
          queue.Enqueue(current.left);
        if(current.right is not null)
          queue.Enqueue(current.right);
      }
      currentDepth++;
    }

    return root;
  }
}