Computes the child 'next l index' array in O(n) based on the LCP table.

        Abouelhoda et al. (2004).

def _compute_childtab_next_l_index(self, lcptab):
        """Computes the child 'next l index' array in O(n) based on the LCP table.

        Abouelhoda et al. (2004).
        """
        stack = [0]
        n = len(lcptab)
        childtab_next_l_index = np.zeros(n, dtype=np.int)  # Zeros / -1 ?
        for i in xrange(n):
            while lcptab[i] < lcptab[stack[-1]]:
                stack.pop()
            if lcptab[i] == lcptab[stack[-1]]:
                last_index = stack.pop()
                childtab_next_l_index[last_index] = i
            stack.append(i)
        return childtab_next_l_index