PSPACE

• SPACE( s(n) ) is the set of languages that can be decided using no more than O( s(n) ) cells of the tape.

• PSPACE = ? SPACE ( nk )

• We can reuse space, but not time.

• So is PSPACE as big than NP?

  • Yes- probably bigger

• Try all possibilities for a solution; we can write over old guesses.

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