Question: A k-head pushdown automaton (k-PDA) is a deterministic pushdown automaton with k read only, two-way input heads and a read/write stack. Define the class PDA

A k-head pushdown automaton (k-PDA) is a deterministic pushdown automaton with k read only, two-way input heads and a read/write stack. Define the class PDA_k = {A| A is recognized by a k-PDA}. Show that P = S ∪_k PDA_k. Recall that P equals alternating log space.

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