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Linear SearchIn computer science, linear search is a search algorithm, also known as sequential search, that is suitable for searching a set of data for a particular value. It operates by checking every element of a list until a match is found. Linear search runs in O(N). If the data are distributed randomly, on average N/2 comparisons will be needed. The best case is that the value is equal to the first element tested, in which case only 1 comparison is needed. The worst case is that the value is not in the list, in which case N comparisons are needed. Here is a sample implementation in Ruby: def linear_search(array, value) for element in array return true if element == value end return false end Here is a sample implementation in PHP: function linear_search($array, $value) { foreach ($array as $current) { if ($current == $value) { return TRUE; } } return FALSE; } Here is another example in Java: public static boolean linear_search(Comparable array, Comparable value) { for(Comparable c : array) { if(c.compareTo(value) == 0) return true; } return false; } And here is a sample implementation in C++ using templates and STL containers: template bool linear_search(const C& array, const T& value) { C::const_iterator iter = array.begin(); C::const_iterator end = array.end(); while (iter != end) { if (*iter == value) return true; ++iter; } return false; } Linear search can be used to search an unordered list. The more efficient binary search can only be used to search an ordered list. If more than a small number of searches are needed, it is advisable to use a more efficient data structure. One approach is to sort and then use binary searches. Another common one is to build up a hash table and then do hash lookups.
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