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Unformatted text preview: 7. The set of all strings not in {a n b n c n  n 1} Generate an error by having too many of one letter. S > TC  UC  AV T > aTb  aT  a ( generates excess as) U > aUb  Ub  b ( generates excess bs) V > bVc  Vc  c ( generates excess cs) A > aA  C > cC  We also need to Union this with all strings not of the form a*b*c*. 8. The set of all strings not in {0100100010000110 n 1  n 1} The idea here is to generate 0 i 10 j as a substring, where i+1 != j. There are two cases, either i >= j, or j >= i+2. S > E1 *  *1E1 * E > T  U (E generates the error) T > 0T0  0T  1 (generates i >= j, too many 0s on the left side) U > V00 (generates j >= i+2, too many 0s on the right side) V > 0V0  V0  1...
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 Fall '06
 HOPCROFT

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