Nodes in a Subtree
You are given a tree that contains N nodes, each containing an integer u which corresponds to a lowercase character c in the string s using 1-based indexing.
You are required to answer Q queries of type [u, c], where u is an integer and c is a lowercase letter. The query result is the number of nodes in the subtree of node u containing c.
Signature
int[] countOfNodes(Node root, ArrayList <<'query' >> queries, String s)
Input
A pointer to the root node, an array list containing Q queries of type [u, c], and a string s
Constraints
N and Q are the integers between 1 and 1,000,000
u is a unique integer between 1 and N
s is of the length of N, containing only lowercase letters
c is a lowercase letter contained in string s
Node 1 is the root of the tree
Output
An integer array containing the response to each query

Example
1(a)
/ ..... \
2(b) 3(a)

s = "aba"
RootNode = 1
query = [[1, 'a']]
Note: Node 1 corresponds to first letter 'a', Node 2 corresponds to second letter of the string 'b', Node 3 corresponds to third letter of the string 'a'.
output = [2]
Both Node 1 and Node 3 contain 'a', so the number of nodes within the subtree of Node 1 containing 'a' is 2.