strStr

今天好像被打开了新世界的大门，这道题也很顺利，查找一个字符串中一段特定的字符串

haystack = "aaa"needle = "aa"sl = len(needle)flag = 0for i in range(len(haystack)-sl + 1):    k = 0    s = []    while k < sl:        s.append(haystack[i+k])        k = k +1    s = ''.join(s)    print(s)    if s == needle:        print(i)        flag = 1if not(flag):    print(-1)