'''
This code explores the KMP algorithm idea,
assuming that the overlap function has been precomputed.
It uses 3 index variables -
i - for current position in T
j -for current position in P
k - start of a potential match
'''
__author__ = "Marina Barsky, and Catherine Liu"

T = 'tictictictactictictic'
P = 'tictic'

#for visualization purposes, we convert the strings to lists of characters
#to better see them in the visualizer: https://goo.gl/iVonii
T = list(T)
P = list(P)

M = len(P)
N = len(T)

of_list = [0, 0, 0, 1, 2, 3]  # manually precomputed overlap function

# algorithm
i = 0 #current position at which to compare character in T
j = 0 #current position at which to compare character in P
k = 0 #start position of a potential match in T

while N - k >= M: #while start position is M characters from the end of T
    #loop while characters match
    while j < M and T[i] == P[j]:
        i = i + 1
        j = j + 1
    if j == M:
        print("Found match at position", (i - M))

    of_prev = of_list[j-1]
    if of_prev == 0:  # not even first character match
        i = i + 1
        k = i
        j = 0
    else:
        k = i - of_prev
        i = k + of_prev
        j = of_prev