leetcode implement strStr python

#kmp
class Solution(object):
def strStr(self, haystack, needle):
"""
:type haystack: str
:type needle: str
:rtype: int
"""
if len(haystack) <= 0 and len(needle)<=0:
return 0

arrNext=self.getNext(needle)
i=0
j=0
intHLen=len(haystack)
intNLen=len(needle)
while i < intHLen and j < intNLen:
if j==-1 or haystack[i] == needle[j]:
i+=1
j+=1
else:
j=arrNext[j]
if j == intNLen:
return i-j
else:
return -1
def getNext(self,needle):
arrNext=dict()
arrNext[0]=-1
k=-1
j=0
intLen=len(needle)
while j < intLen:
if k==-1 or needle[k] == needle[j]:
k+=1
j+=1
arrNext[j]=k
else:
k=arrNext[k]
return arrNext