function COMPARE(X, Y : Array) : R

s ← e, i ← 1, j ← 1

while(i ≤ |X| or j ≤ |Y|) :

x ← X [i], y ← Y[j]

if((y = NIL)‖(word[x] = word[y])) :

s ← s + d(phi[x], 0)

i ← (i + 1)

elseif((x = NIL)or(word[x] > word[y])) :

s ← (s + d(0, ϕ[y]))

j ← (j + 1)

else :

s ← (s + d(ϕ[x],ϕ[y]))

i ← (i + 1), j ← (j + 1)

returns