[leetcode:python]28.Implement strStr()

题目：实现strStr()
Returns the index of the first occurrence of needle in haystack, or -1 if needle is not part of haystack.
题意：
子字符串在字符串中第一次匹配的位置，如果不能匹配返回-1

方法一：性能65ms

class Solution(object):    def strStr(self, haystack, needle):        """        :type haystack: str        :type needle: str        :rtype: int        """        if not needle and not haystack:            return 0        if not needle:            return 0        if not haystack and needle:            return -1        ans = -1        i, hay = 0, len(haystack)        k, nee = 0, len(needle)        for i in xrange(hay):            if haystack[i] == needle[k]:                ans = i                s = i+1                for k in xrange(1, nee):                    if s >= hay:                        return -1                    if haystack[s] != needle[k]:                        ans = -1                        k = 0                        break                    s+=1                if ans != -1:                    return ans        return ans

方法二：性能42ms

class Solution(object):    def strStr(self, haystack, needle):        """        :type haystack: str        :type needle: str        :rtype: int        """        return haystack.find(needle)

使用haystack包的find()函数