Ejemplo n.º 1
0
def fundamental_preprocess(S):
    if len(S) == 0: # Handles case of empty string
        return []
    if len(S) == 1: # Handles case of single-character string
        return [1]
    z = [0 for x in S]
    z[0] = len(S)
    z[1] = match_length(S, 0, 1)
    for i in range(2, 1+z[1]): # Optimization from exercise 1-5
        z[i] = z[1]-i+1
    # Defines lower and upper limits of z-box
    l = 0
    r = 0
    for i in range(2+z[1], len(S)):
        if i <= r: # i falls within existing z-box
            k = i-l
            b = z[k]
            a = r-i+1
            if b < a: # b ends within existing z-box
                z[i] = b
            elif b > a: # Optimization from exercise 1-6
                z[i] = min(b, len(S)-i)
                l = i
                r = i+z[i]-1
            else: # b ends exactly at end of existing z-box
                z[i] = b+match_length(S, a, r+1)
                l = i
                r = i+z[i]-1
        else: # i does not reside within existing z-box
            z[i] = match_length(S, 0, i)
            if z[i] > 0:
                l = i
                r = i+z[i]-1
    return z
Ejemplo n.º 2
0
 def check(self, S, idx1, idx2, expected):
     self.longMessage = True
     info = 'S - \"%s\", idx1 - %d, idx2 - %d' %(S, idx1, idx2)
     self.assertEqual(expected, match_length(S, idx1, idx2), msg=info)