Deepest Leaves Sum

Easy

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Average time to solve is 15m

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Problem statement

You have been given a binary tree of integers. Your task is to calculate the sum of all the leaf nodes which are present at the deepest level of this binary tree. If there are no such nodes, print 0.

NOTE: The deepest level of a binary tree is the level which is present at the maximum depth from the root node.

Follow up:

Can you solve this problem in a single traversal of the binary tree?

Detailed explanation ( Input/output format, Notes, Images )

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 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 will 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:

For each test case, print the sum of all the leaf nodes present at the deepest level of the given binary tree.

Print the output of each test case in a separate line.

Note:

You are not required to print the expected output, it has already been taken care of. Just implement the function.

Constraints:

1 <= T <= 10^2
0 <= N <= 3000  
Where N is the number of nodes in the binary tree

The sum will always fit in a 32-bit integer.    

Time Limit: 1 sec

Sample Input 1:

3
71 2 16 110 -1 -1 5 -1 -1 -1 -1
1 2 3 4 5 6 7 -1 -1 -1 -1 -1 -1 -1 -1
-1

Sample Output 1:

115 
22
0

Explanation of Sample Input 1:

For the first test case, we have nodes 110 and 5 present at the deepest level of the binary tree. So the sum will be 110 + 5 = 115.

For the second test case, we have nodes 4, 5, 6 and 7 present at the deepest level of the binary tree.

For the third test case, we don't have any such nodes. So the sum will be 0.

Sample Input 2:

2
1 2 3 4 -1 5 -1 -1 -1 -1 -1
1 2 -1 3 -1 4 -1 -1 -1

Sample Output 2:

9
4

Console