gistfile1.clj

(defn trim-head [coll]                                                          
  (loop [so-far [], indexes {}, index 0, coll (seq coll)]                       
    (if-not coll                                                                
      {:origin nil, :pattern so-far} ;; ?? not specified in question            
      (let [x (first coll), xs (rest coll)]                                     
        (if (contains? indexes x)                                               
          {:origin (subvec so-far 0 (indexes x))                                
           :pattern (subvec so-far (indexes x))}                                
          (case x                                                               
            0 {:origin so-far, :pattern [x]}                                    
            1 {:origin nil, :pattern (conj so-far x)}                           
            (recur (conj so-far x) (assoc indexes x index) (inc index) (seq xs)\
)))))))