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A searching algorithm is an algorithm that aims to find an item within a collection of items.
There are many kinds of searching algorithms, including:
- list search algorithms, which search for an item in a linear (one-dimensional) collection, for example, an array.
- linear search, searches any list, runs in O(n). Typically a search like this would use a loop to iterate through the list until the required item was found.
- binary search, searches a sorted list, runs in O(log n).
- tree searching algorithms, which search for an item in a tree.
- string searching algorithms, which search for patterns within strings
Bash
function in_array {
for i in "${@:2}"; do
[[ "$i" == "$1" ]] && return 0
done
}
haystack=("apple" "orange" "yellow banana")
in_array "orange" "${haystack[@]}" && echo found || echo not found
Go
func in_array(needle interface{}, haystack []interface{}) (exists bool) {
for i := range haystack {
if exists = haystack[i] == needle; exists {
return
}
}
return
}
Java
Java implements the binary search in both the Collections and Arrays classes.
JavaScript
From all modern browsers and IE9+ you can use Array.prototype.indexOf():
var present = haystack.indexOf(needle) > -1;
You can either polyfill the standard function with the above mentioned MDN article on indexOf() or use a simpler version:
function in_array(needle,haystack) {
if(!haystack instanceof Array) throw 'Error: Haystack isn\'t an array.';
for(var i in haystack) if(haystack[i]==needle) return true;
return false;
}
Or if you use jQuery anyways:
var present = $.inArray(needle, haystack) > -1;
Perl
if(grep $_ eq $needle, @haystack) {
print "Success!";
}