CS 475 Midterm: CS 475 Alabama Fall2017 Exam2 2Solutions
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You may choose any set of problems that adds up to 100 or more points: write all the strings of length 6 that are generated by this context-free grammar. Solution a parse tree for each such string. [30 points for cs 475] [20 points for cs 575] T v d t f v c d t f. V c: write all the strings of lengths 3 and 6 that are accepted by this pushdown automaton. Hint: first get the strings of length 3, then use these to get the strings of length 6. [30 points for cs 475] [20 points for cs 575] a, /vw b, /t c, /u f, x/ g, v/ h, w/ . , z0/ e, / j, t/ k, / . Alternatively, write an ambiguous cfg for this language. Hint: the number of a"s must be either more or less than the number of b"s. S atbs | bvas | ax | by.
