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100 lines
3.3 KiB
Python
100 lines
3.3 KiB
Python
"""
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This is pure python implementation of interpolation search algorithm
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"""
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from __future__ import print_function
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import bisect
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try:
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raw_input # Python 2
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except NameError:
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raw_input = input # Python 3
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def interpolation_search(sorted_collection, item):
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"""Pure implementation of interpolation search algorithm in Python
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Be careful collection must be sorted, otherwise result will be
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unpredictable
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:param sorted_collection: some sorted collection with comparable items
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:param item: item value to search
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:return: index of found item or None if item is not found
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"""
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left = 0
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right = len(sorted_collection) - 1
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while left <= right:
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point = left + ((item - sorted_collection[left]) * (right - left)) // (sorted_collection[right] - sorted_collection[left])
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#out of range check
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if point<0 or point>=len(sorted_collection):
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return None
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current_item = sorted_collection[point]
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if current_item == item:
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return point
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else:
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if item < current_item:
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right = point - 1
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else:
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left = point + 1
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return None
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def interpolation_search_by_recursion(sorted_collection, item, left, right):
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"""Pure implementation of interpolation search algorithm in Python by recursion
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Be careful collection must be sorted, otherwise result will be
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unpredictable
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First recursion should be started with left=0 and right=(len(sorted_collection)-1)
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:param sorted_collection: some sorted collection with comparable items
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:param item: item value to search
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:return: index of found item or None if item is not found
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"""
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point = left + ((item - sorted_collection[left]) * (right - left)) // (sorted_collection[right] - sorted_collection[left])
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#out of range check
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if point<0 or point>=len(sorted_collection):
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return None
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if sorted_collection[point] == item:
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return point
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elif sorted_collection[point] > item:
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return interpolation_search_by_recursion(sorted_collection, item, left, point-1)
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else:
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return interpolation_search_by_recursion(sorted_collection, item, point+1, right)
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def __assert_sorted(collection):
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"""Check if collection is sorted, if not - raises :py:class:`ValueError`
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:param collection: collection
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:return: True if collection is sorted
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:raise: :py:class:`ValueError` if collection is not sorted
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Examples:
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>>> __assert_sorted([0, 1, 2, 4])
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True
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>>> __assert_sorted([10, -1, 5])
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Traceback (most recent call last):
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...
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ValueError: Collection must be sorted
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"""
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if collection != sorted(collection):
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raise ValueError('Collection must be sorted')
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return True
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if __name__ == '__main__':
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import sys
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user_input = raw_input('Enter numbers separated by comma:\n').strip()
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collection = [int(item) for item in user_input.split(',')]
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try:
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__assert_sorted(collection)
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except ValueError:
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sys.exit('Sequence must be sorted to apply interpolation search')
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target_input = raw_input('Enter a single number to be found in the list:\n')
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target = int(target_input)
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result = interpolation_search(collection, target)
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if result is not None:
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print('{} found at positions: {}'.format(target, result))
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else:
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print('Not found')
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