1.Linear
search or sequential search is a method for finding a
particular value in a list that consists of checking every one of its elements,
one at a time and in sequence, until the desired one is found.
·Linear search is the simplest search
algorithm. For a list with n items, the best case is when the value is equal to
the first element of the list, in which case only one comparison is needed. The
worst case is when the value is not in the list (or occurs only once at the end
of the list), in which case n comparisons are needed.
·Linear searches don't require the
collection to be sorted.
2. A binary search or half-interval search algorithm finds
the position of a specified value (the input "key") within a sorted
array. In each step, the algorithm compares the input key value with the key
value of the middle element of the array. If the keys match, then a matching
element has been found so its index, or position, is returned. Otherwise, if
the sought key is less than the middle element's key, then the algorithm
repeats its action on the sub-array to the left of the middle element or, if
the input key is greater, on the sub-array to the right. If the remaining array
to be searched is reduced to zero, then the key cannot be found in the array
and a special "Not found" indication is returned.
· Every iteration eliminates half of
the remaining possibilities. This makes binary searches very efficient - even for
large collections.
· Binary search requires a sorted
collection. Also, binary searching can only be applied to a collection that
allows random access (indexing).
·Worst case performance: O(log n)
· Best case performance: O(1)
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