Track Highest-Earning Experience

You are building a core component for a real-time analytics system that tracks the profitability of experiences on a large online platform.

Implement a function that processes a sequence of operations and returns the result of each query.

You are given three arrays of equal length:

• operations[i] : either 'U' for an update or 'Q' for a query
• experiences[i] : the name of the experience involved in operation i
• deltas[i] : the profit change for the experience if operations[i] == 'U' ; otherwise this value is ignored

Rules:

• For an update operation 'U' , add deltas[i] to the current total earnings of experiences[i]
• For a query operation 'Q' , return the name of the experience with the highest total earnings at that moment
• If an experience has not been updated before, treat its earnings as 0 before applying its first update
• If multiple experiences are tied for the highest earnings, returning any one of them is acceptable
• You may assume each query happens after at least one update

Return an array containing the answers for all query operations, in order.

Example:

• operations = ['U', 'U', 'Q', 'U', 'Q']
• experiences = ['GameA', 'GameB', '', 'GameA', '']
• deltas = [5, 7, 0, 4, 0]

Processing:

• Update GameA by +5 → totals: GameA = 5
• Update GameB by +7 → totals: GameB = 7
• Query → return GameB
• Update GameA by +4 → totals: GameA = 9
• Query → return GameA

Output: ['GameB', 'GameA']

Design an efficient solution for processing many updates and queries.