Find the longest common starting substring in a set of strings [closed]

Answer 1

You just need to traverse all strings until they differ, then take the substring up to this point.

Pseudocode:

loop for i upfrom 0
     while all strings[i] are equal
     finally return substring[0..i]

Common Lisp:

(defun longest-common-starting-substring (&rest strings)
  (loop for i from 0 below (apply #'min (mapcar #'length strings))
     while (apply #'char=
                  (mapcar (lambda (string) (aref string i))
                          strings))
     finally (return (subseq (first strings) 0 i))))