www.altavista.digital.com gave the following URL:

http://pascal.math.yorku.c

The code is some kind of Pascal but you get the drift and translation to C should not be difficult.

Procedure Ternary( [a_1, ..., a_n]: sorted list; x: number)

l:=1, r:=n

while l < r

begin

k := floor(r+l /3) { note k is equal l + floor(r-l /3) }

if x > a_k

then { x is not in first third }

begin

k' := floor(2(r+l) /3)

{ and k' is l + 2* floor(r-l /3) }

if x > a_k'

then

l:= k' +1 { since x not in first 2 thirds }

else { x not in first or last third }

begin

l := k+1

r := k'

end

else r := k { first third is only possibility }

end { when this is done l = r and x = a_r or not in list }

if x = a_r then A := 1

else A := 0

output A