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Given a list of alert codes alerts and a list of required alert codes required, return the shortest contiguous subarray of alerts that contains every code from required with at least the same frequency. If no such subarray exists, return an empty list. The function should return the subarray values, not the indices.
1 <= len(alerts) <= 10^51 <= len(required) <= 10^5alerts[i] and required[i] are non-empty strings2 * 10^5