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