Longest Repeated SubString

lrss.py

def lrss(s):
    slen = len(s)
    for l in range(slen - 1, 1, -1): # the length of the string, go from max to min, decrementing range
        print "l=" + str(l)
        # there is a bit of redundancy in the i/j iterations as they double check each other
        # e.g. when i < j and j > i
        for i in range(0, slen - l + 1): # tracks position of the iterations
            print "  i=" + str(i)
            for j in range(0, slen - l + 1): # tracks position of the iterations
                if i == j: continue # if i == j , then it's the same index in the string
                print "    j=" + str(j)
                for k in range(0, l):
                    print "       k=" + str(k)
                    if s[i + k] != s[j + k]: # stop checking!
                        break
                    if k == l - 1: # at this point we know they are equal,
                                 # so lets determine if this is the last character to check
                        print "found match at i=" + str(i) + ", j=" + str(j) + " of length=" + str(l)
                        return s[i : i + l] # return substring, s[from index, to index]
    return None


print lrss('banana') # ana
print lrss('bananaisbanana') # banana
print lrss('abcdefg') # None

# the l,i,j iterations seemed sane after i added + 1 to the i/j ranges
# prior to adding the + 1 to ranges i noticed it was not checking all the i/j cases i expected
# l=5
#   i=0
#     j=1
#   i=1
#     j=0
# l=4
#   i=0
#     j=1
#     j=2
#   i=1
#     j=0
#     j=2
#   i=2
#     j=0
#     j=1
# l=3
#   i=0
#     j=1
#     j=2
#     j=3
#   i=1
#     j=0
#     j=2
#     j=3
#   i=2
#     j=0
#     j=1
#     j=3
#   i=3
#     j=0
#     j=1
#     j=2
# l=2
#   i=0
#     j=1
#     j=2
#     j=3
#     j=4
#   i=1
#     j=0
#     j=2
#     j=3
#     j=4
#   i=2
#     j=0
#     j=1
#     j=3
#     j=4
#   i=3
#     j=0
#     j=1
#     j=2
#     j=4
#   i=4
#     j=0
#     j=1
#     j=2
#     j=3


# after adding the k logging i noticed that the k's are not being iterated as much as i'd expect
# also we could stop checking earlier once s[i + k] != s[j + k], so i'll rewrite that

# current output with ks without fixing the off-by-one error
# l=5
#   i=0
#     j=1
#        k=0
#        k=1
#        k=2
#        k=3
#   i=1
#     j=0
#        k=0
#        k=1
#        k=2
#        k=3
# l=4
#   i=0
#     j=1
#        k=0
#        k=1
#        k=2
#     j=2
#        k=0
#        k=1
#        k=2
#   i=1
#     j=0
#        k=0
#        k=1
#        k=2
#     j=2
#        k=0
#        k=1
#        k=2
#   i=2
#     j=0
#        k=0
#        k=1
#        k=2
#     j=1
#        k=0
#        k=1
#        k=2
# l=3
#   i=0
#     j=1
#        k=0
#        k=1
#     j=2
#        k=0
#        k=1
#     j=3
#        k=0
#        k=1
#   i=1
#     j=0
#        k=0
#        k=1
#     j=2
#        k=0
#        k=1
#     j=3
#        k=0
#        k=1
#   i=2
#     j=0
#        k=0
#        k=1
#     j=1
#        k=0
#        k=1
#     j=3
#        k=0
#        k=1
#   i=3
#     j=0
#        k=0
#        k=1
#     j=1
#        k=0
#        k=1
#     j=2
#        k=0
#        k=1
# l=2
#   i=0
#     j=1
#        k=0
#     j=2
#        k=0
#     j=3
#        k=0
#     j=4
#        k=0
#   i=1
#     j=0
#        k=0
#     j=2
#        k=0
#     j=3
#        k=0
#     j=4
#        k=0
#   i=2
#     j=0
#        k=0
#     j=1
#        k=0
#     j=3
#        k=0
#     j=4
#        k=0
#   i=3
#     j=0
#        k=0
#     j=1
#        k=0
#     j=2
#        k=0
#     j=4
#        k=0
#   i=4
#     j=0
#        k=0
#     j=1
#        k=0
#     j=2
#        k=0
#     j=3
#        k=0

# after adding + 1 to k range it output
# l=5
#   i=0
#     j=1
#        k=0
#        k=1
#        k=2
#        k=3
#        k=4
#   i=1
#     j=0
#        k=0
#        k=1
#        k=2
#        k=3
#        k=4
# l=4
#   i=0
#     j=1
#        k=0
#        k=1
#        k=2
#        k=3
#     j=2
#        k=0
#        k=1
#        k=2
#        k=3
# found match at i=0, j=2 of length=4
# bana

# this is closer! the k's look good, BUT notice how the result is WRONG
# this is simply because the FIRST time that s[i + k] != s[j + k], we should BREAK.
# i know we discussed this despite not coding it on the board
# basically what happened is that s[i + k] == s[j + k] where k == l, so the last character matched.
#  this is why you want to break early whne the characters are not equal

# after those changes, we get the result!
# l=5
#   i=0
#     j=1
#        k=0
#   i=1
#     j=0
#        k=0
# l=4
#   i=0
#     j=1
#        k=0
#     j=2
#        k=0
#   i=1
#     j=0
#        k=0
#     j=2
#        k=0
#   i=2
#     j=0
#        k=0
#     j=1
#        k=0
# l=3
#   i=0
#     j=1
#        k=0
#     j=2
#        k=0
#     j=3
#        k=0
#   i=1
#     j=0
#        k=0
#     j=2
#        k=0
#     j=3
#        k=0
#        k=1
#        k=2
# found match at i=1, j=3 of length=3
# ana

# i next went back and added more test examples and added spacing between certain characters