1、题目
Given an array of strings, group anagrams together. For example, given: ["eat", "tea", "tan", "ate", "nat", "bat"],
Return: [
["ate", "eat","tea"],
["nat","tan"],
["bat"]
]
Note: All inputs will be in lower-case.
2、分析，该题目可以针对每个字符串进行排序，然后计算每个字符串的hash值进行归类
3、优化、在计算hash值的时候，考虑hash算法跟字符串排序无关，也就是不用进行排序，针对26个字母分配26个质数，然后将hash函数设置为每个字母映射的质数乘积，便不用进行排序了，该方法利用了质数的特性
两个质数相乘得到一个合数，这个合数不会分解为其它质数的乘积
4、代码：
#!/usr/local/bin/python3
# -*- coding: utf-8 -*-
__author__ = 'qqvipfunction' primeTable = [2,3,5,7,11, 13,17,19,23,29, 31,37,41,43,47, 53,59,61,67,71, 73,79,83,89,97, 101] class Solution(object): def groupAnagrams(self, strs):
"""
:type strs: List[str]
:rtype: List[List[str]]
"""
map = {}
for i in range(0 , len(strs)):
str = strs[i]
hash = self.hash_str(str)
list = map.get(hash, None)
if not list:
list = []
list.append(str)
map[hash] = list return map.values() def hash_str(self, str):
length = len(str)
charAvalue = ord('a')
if length > 0:
hashSum = 1
for i in range(0, length):
hashSum = hashSum * primeTable[(ord(str[i]) - charAvalue)]
return hashSum
return 0 if __name__ == '__main__':
s = Solution()
print(s.groupAnagrams(["eat", "tea", "bat"]))