kneedle in a knapsack i.e. substring prblem

indexof

#!/usr/local/bin/python2.7
  
def strstr_brute(string,pattern):
  if string and pattern :
    N,K=len(string),len(pattern)
    for i in range(N-K+1):
      if string[i:i+K] == pattern:
        return i
  return -1

def find_hash_char(charecter):
  return ord(charecter)

def find_hash(string):
  hashVal=0
  for char in string:
    hashVal+=ord(char)
  return hashVal

def strstr_rabinkarp(string,pattern):
  if string and pattern:
    N,K=len(string),len(pattern)
    firstHash=find_hash(string[0:K])
    pattHash=find_hash(pattern)
    hashV=firstHash
    for i in xrange(N-K+1):
      if hashV==pattHash and string[i:i+K]==pattern:
        return i
      hashV=hashV-find_hash_char(string[i])+find_hash_char(string[i+K])
  return -1  

print strstr_brute("kishan","an")
print strstr_rabinkarp("kishan","an")