A Collection of Code Snippets in as Many Programming Languages as Possible

This project is maintained by TheRenegadeCoder

Welcome to the Binary Search in Mathematica page! Here, you’ll find the source code for this program as well as a description of how the program works.

```
(* Code *)
(* Binary search option binarySearch1 uses the built-in, modified to
return Null in case the element is not found: *)
Needs["Combinatorica`"]
binarySearch1 = If[IntegerQ[#], #, Null] & @*
Combinatorica`BinarySearch;
(* If that is considered cheating, then option binarySearch2 implements it
using 'primitives': *)
binarySearch2 = Function[{l, n},
NestWhile[ (* keep subdividing the search interval *)
Apply[(* convert the single two-element list argument to two arguments *)
Function[{i, j},(* subdivide the given interval into a smaller one containing the item sought *)
Module[{m = Floor[(i + j)/2], me},(* use some definite element as the midpoint to test *)
me = l[[m]];
Which[
(* Did we find the element we're searching for? *)
me == n, m,
(* Element is before the midpoint? Then either keep searching, or give up *)
n < me, If[i < m, {i, m - 1}, Null],
(* Element is after the midpoint? Then either keep searching, or give up *)
n > me, If[m < j, {m + 1, j}, Null]]]]],
{1, Length[l]} (* begin by considering the entire list to search within *),
ListQ (* while we are still searching *)]];
(* The outer function does the string parsing: *)
binarySearchMain = Function[{l, i},
Module[{e = "Usage: please provide a list of sorted integers (\"1, 4, 5, 11, 12\") and the integer to find (\"11\")"},
Catch[
If[
(* convert position to "true" or Null to "false" *)
IntegerQ[binarySearch2 @@ Map[
(* convert string to integer, or throw *)
s \[Function] If[StringMatchQ[s, DigitCharacter ..],
FromDigits[s],
Throw[e]],
(* construct two arguments to binary search: list of search array, item to search; as strings *)
{StringSplit[If[StringLength[l] > 0, l, Throw[e]], ", "], i},
{-1} (* at each leaf *)]],
"true", "false"]]]];
(* Valid Tests *)
Print /@ Apply[binarySearchMain] /@ {
{"1, 4, 5, 11, 12", "4"},
{"1, 3, 5, 7", "1"},
{"1, 3, 5, 7", "7"},
{"5", "5"},
{"5", "7"},
{"1, 3, 5, 6", "7"}};
(* Invalid Tests *)
binarySearchMain["1, 2, 3, 4",""]
binarySearchMain["", "5"]
(* Not checking the 'list is unsorted' invalid test. *)
```

Binary Search in Mathematica was written by:

- Ben Hekster

If you see anything you’d like to change or update, please consider contributing.

No ‘How to Implement the Solution’ section available. Please consider contributing.

No ‘How to Run the Solution’ section available. Please consider contributing.