4

Leaves One Level Apart

Difficulty: MEDIUM
Contributed By
Prateek Kalyani
Avg. time to solve
40 min
Success Rate
60%

Problem Statement
Suggest Edit

You are given a binary tree of 'N' nodes. Your task is to print 'True' if the leaves of the tree are at most one level apart else print 'False'.

Input Format :
The first line of input contains an integer 'T' representing the number of test cases. Then the test cases follow.

The only line of each test case contains elements 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 on its place.

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

Example Input

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 :
For each test case, print "True" if the leaves of the tree are at most one level apart else print "False".

The output of each test case will be printed in a separate line.
Note :
You don't need to print anything. It has already been take care of, just implement the given function.
Constraints :
1 <= T <= 2*10^2
0 <= N <= 3*10^3
0 <= NODE.DATA <= 10^5

Time Limit : 1 sec
Sample Input 1 :
1
5 6 2 4 3 -1 -1 9 7 -1 -1 -1 -1 -1 -1
Sample Output 1 :
False
Explanation For Sample Input 1 :

Sample Input 1

The leaves (2, 7) and (2, 9) are two levels apart, thus the answer is False.
Sample Input 2 :
2
2 3 4 -1 -1 -1 -1
8 -1 -1
Sample Output 2 :
True
True
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