Leetcode 28 Implement strStr()

暴力匹配，时间复杂度为O(n*n)，建议KMP

class Solution:
    # @param {string} haystack
    # @param {string} needle
    # @return {integer}
    def strStr(self, haystack, needle):
        if len(haystack) < len(needle): return -1
        i = 0
        while i < len(haystack)-len(needle)+1:
            j=i;k=0
            while k < len(needle):
                if haystack[j] == needle[k]: j+=1; k+=1
                else: break
            if k == len(needle): break
            else:i+=1
        if i==(len(haystack)-len(needle)+1): return -1
        else: return i