 Print Nodes having K leaves
Medium Accuracy: 40.38% Submissions: 9601 Points: 4

Given a binary tree and a integer value K, the task is to find all nodes data in given binary tree having exactly K leaves in sub-tree rooted with them.

NOTE: Nodes should be printed in the order in which they appear in postorder traversal.

Example 1:

Input:
K = 1
0
/   \
1     2
Output: -1
Explanation: There is no node in this
tree which has one leaf in the sub tree
below it.


Example 2:

Input:
K = 2
0
/   \
1     2
/
4
/   \
5     9
Output: 4 2
Explanation: Nodes with data 2 and 4, have
2 leaves in the subtree below it.

Just complete the function btWithKleaves() and returns the answer (as a vector<int> in cpp, as a ArrayList<Integer> in java and as list in python)

Note: If no node is found the list returned should contain only one value -1.
Expected Time Complexity: O(N).
Expected Auxiliary Space: O(Height of the Tree).

Constraints:
1 <= N <= 1000
1 <= K <= 1000
1 <= value of nodes <= 10000

Note:The Input/Ouput format and Example given are used for system's internal purpose, and should be used by a user for Expected Output only. As it is a function problem, hence a user should not read any input from stdin/console. The task is to complete the function specified, and not to write the full code. 