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ChapLeo
ok, I'm not quite sure whether I can ask this question, but I don't understand the solution given for the 6th question in Quiz 2. Following is the algorithm I wrote for the cmpGuess function (in order to check my own solution): def cmpGuess(guess): """ Assumes that guess is an integer in range(maxVal). Returns -1 if guess is < magic number, 0 if ==, 1 if > """ magicNumber =4 if guess < magicNumber: return -1 if guess > magicNumber: return 1 if guess == magicNumber: return 0 Is my understanding of the specification of the function right or wrong?
It'll return those values, 1 for higher than 4, 0 equal to 4, -1 less than 4.
That is what I thought as well. The following is the coding given in the solution sheet for question 6 of Quiz 2. Integrating this coding with the above coding doesn't result in the expected solution to the problem. e.g.: if the statement "findNumber(50)" is given, the answer returned is 49, not 4, as it should be. Is the solution given in the marking scheme wrong? or is my coding wrong? Can you please explain this? Thanks def findNumber(maxVal): """ Assumes that maxVal is a positive integer. Returns a number, num, such that cmpGuess(num) == 0 """ s = range(0, maxVal) return bsearch(s, 0, len(s) -1) def bsearch(s, first, last): if (last -first) < 2: if cmpGuess(s[first]) == 0: return first else: return last mid = first + (last -first)/2 if cmpGuess(s[mid]) == 0: return s[mid] if cmpGuess(s[mid]) == -1: return bsearch(s, first, mid -1) return bsearch(s, mid + 1, last)