Print All The Nodes At Distance K From The Given Node

You have been given a Binary Tree of distinct integers and two integers “target” and ‘K’. You are supposed to return the list of values of all the nodes which are situated at ‘K’ distance from the target node.

Distance between two nodes ‘u’ and ‘v’ is defined as the number of edges in the shortest path from ‘u’ to ‘v’.

Note :

You may assume that the given target node definitely exists in the given binary tree.

For example :

For the given binary tree

Nodes in the above binary tree that has K = 2 distance from the target node are highlighted in yellow colour.

Input Format :

The first line contains an integer 'T' which denotes the number of test cases or queries to be run. Then the test cases are as follows.

The first line of each test case contains elements of the tree in the level order form. The line consists of values of nodes separated by a single space. In case a node is null, we take -1 in its place.

The second line of each test case contains two integers “target” and ‘K’ which are described above.

For example, the input for the tree depicted in the below image would be :

1
2 3
4 -1 5 6
-1 7 -1 -1 -1 -1
-1 -1

Explanation :

Level 1 :
The root node of the tree is 1

Level 2 :
Left child of 1 = 2
Right child of 1 = 3

Level 3 :
Left child of 2 = 4
Right child of 2 = null (-1)
Left child of 3 = 5
Right child of 3 = 6

Level 4 :
Left child of 4 = null (-1)
Right child of 4 = 7
Left child of 5 = null (-1)
Right child of 5 = null (-1)
Left child of 6 = null (-1)
Right child of 6 = null (-1)

Level 5 :
Left child of 7 = null (-1)
Right child of 7 = null (-1)

The first not-null node(of the previous level) is treated as the parent of the first two nodes of the current level. The second not-null node (of the previous level) is treated as the parent node for the next two nodes of the current level and so on.
The input ends when all nodes at the last level are null(-1).

Note :

The above format was just to provide clarity on how the input is formed for a given tree. 
The sequence will be put together in a single line separated by a single space. Hence, for the above-depicted tree, the input will be given as:

1 2 3 4 -1 5 6 -1 7 -1 -1 -1 -1 -1 -1

Output Format :

Print a list of space-separated integers that denote the values of nodes that are at ‘K’ distance from the “target” node.

For each test case, print the output in a separate line.

Note :

You do not need to print anything; it has already been taken care of. Just implement the given function.

Constraints :

1 <= T <= 100
0 <= N <= 3000
0 <= data <= 10^4
0 <= target <= 1o^4
1 <= K <= 3000

Where ‘N’ is the total number of nodes in the binary tree, and “data” is the value of the binary tree node.

Time Limit: 1sec