Given a binary tree, find the largest value in each level.
Example 1:
Input :
1
/ \
2 3
Output : 1 3
Explanation :
There are two levels in the tree :
1. {1}, max = 1
2. {2, 3}, max = 3
Example 2:
Input :
4
/ \
9 2
/ \ \
3 5 7
Output : 4 9 7
Explanation :
There are three levels in the tree:
1. {4}, max = 4
2. {9, 2}, max = 9
3. {3, 5, 7}, max=7
Your task :
You don't need to read input or print anything. Your task is to complete the function largestValues() which takes the root node of the tree as input and returns a vector containing the largest value in each level.

Expected Time Complexity : O(n) , where n = number of nodes
Expected Auxiliary Space : O(n) , where n = number of nodes

Constraints :
1 ≤ Number of nodes ≤ 10^5

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