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January 9, 2017 22:01
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Challenge for creating an iterator for a list of lists in python for an interview challenge
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| ''' | |
| Challenge: Create an iterator for a list of lists with the following methods: | |
| boolean **hasNext**() | |
| return true if there is another element in the set | |
| int **next**() | |
| return the value of the next element in the array | |
| void **remove**() | |
| remove the last element returned by the iterator. | |
| That is, remove the element that the previous **next()** returned | |
| This method can be called only once per call to **next()**, | |
| otherwise an exception will be thrown. | |
| Given: [[4],[1,2,3],[4,5],[],[],[6],[7,8],[],[9],[10],[]] | |
| Print: 1 2 3 4 5 6 7 8 9 10 | |
| ''' | |
| class arrayIter: | |
| def __init__(self, lst): | |
| self.array = lst | |
| self.i = -1 | |
| self.j = -1 | |
| self.prev_i = 0 | |
| self.prev_j = 0 | |
| def isEmpty(self): | |
| return (len(self.array[self.i]) == 0) | |
| def incrementPointer(self): | |
| self.prev_i = self.i | |
| self.prev_j = self.j | |
| while (self.i < len(self.array) - 1): | |
| if (self.j < len(self.array[self.i]) - 1): | |
| self.j += 1 | |
| else: | |
| self.j = 0 | |
| self.i += 1 | |
| if (self.isEmpty() == False): | |
| return | |
| def hasNext(self): | |
| self.incrementPointer() | |
| if (self.i < len(self.array) - 1): | |
| self.i = self.prev_i | |
| self.j = self.prev_j | |
| return True | |
| else: | |
| return False | |
| def next(self): | |
| if (self.hasNext()): | |
| self.incrementPointer() | |
| return self.array[self.i][self.j] | |
| else: | |
| print "ERROR! No next value" | |
| return None | |
| def remove(self): | |
| if (self.i == -1 and self.j == -1): | |
| print "ERROR" | |
| else: | |
| del self.array[self.i][self.j] | |
| self.j -= 1 | |
| def printElements(lst): | |
| obj = arrayIter(lst) | |
| while (obj.hasNext()): | |
| print obj.next() | |
| a = [[],[1,2,3],[4,5],[],[],[6],[7,8],[],[9],[10],[]] | |
| printElements(a) | |
| obj = arrayIter(a) | |
| print obj.next() | |
| print "before:", obj.array | |
| obj.remove() | |
| print "after:", obj.array |
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