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

It's a matter of taste, but this is a simple javascript version: It sorts the array, and then looks just at the first and last items.

//longest common starting substring in an array

function sharedStart(array){
    var A= array.concat().sort(), 
    a1= A[0], a2= A[A.length-1], L= a1.length, i= 0;
    while(i<L && a1.charAt(i)=== a2.charAt(i)) i++;
    return a1.substring(0, i);
}

DEMOS

sharedStart(['interspecies', 'interstelar', 'interstate'])  //=> 'inters'
sharedStart(['throne', 'throne'])                           //=> 'throne'
sharedStart(['throne', 'dungeon'])                          //=> ''
sharedStart(['cheese'])                                     //=> 'cheese'
sharedStart([])                                             //=> ''
sharedStart(['prefix', 'suffix'])                           //=> ''

In Python:

>>> from os.path import commonprefix
>>> commonprefix('interspecies interstelar interstate'.split())
'inters'