Searching string for character in binary search

[Seb]

On Sunday, 25 February 2018 at 21:18:55 UTC, Joel wrote:
> The number tests work, but not the string one.
>
> void main() {
> 	assert([1,2,3,4,5,6,7,8,9,10,11].binarySearch(6));
> assert(! [1,2,3,4,5,7,8,9,10,11].binarySearch(6));
> assert("abcdefghijklmnopqrstuvwxyz".binarySearch('j')); // not 
> work
> 	import std.stdio;
> 	writeln("Assert tests passed!");
> }
>
> bool binarySearch(T)(T[] arr, T n) {
> 	while(arr.length) {
> 		auto i = arr.length/2;
> 		if (arr[i] == n)
> 			return true;
> 		else
> 			if (arr[i]  > n)
> 				arr = arr[i + 1 .. $];
> 			else
> 				arr = arr[0 .. i];
> 	}
> 	return false;
> }



Your cases are wrong:

---
if (arr[i]  > n) // 'n' > 'j'
// The current element is higher than the needle -> you need to 
go to the left, not right
--


-> Swap them.


Also note that Phobos comes with binary search built-in:

---
assert([1,2,3,4,5,6,7,8,9,10,11].assumeSorted.canFind(6));
---

https://run.dlang.io/is/bfpBpA