在散列中,链接法是一种最简单的碰撞解决技术,这种方法的原理就是把散列到同一槽中的所有元素
都放在一个链表中。
链接法有两个定理,定理一:
在简单一致散列的假设下,一次不成功查找的期望时间为O(1 + n)
定理二:
在简单一致散列的假设下,平均情况下一次成功的查找需要的时间为O(1 + n)
该方法使用python的实现如下:
# keys函数 #!/usr/bin/env python # coding=utf-8 class Dict: def __init__(self, num): self.__solts__ = [] self.num = num for _ in range(num): self.__solts__.append([]) def hash_fun(self,key,num): hashval = 0 x = key if x < 0: print "the key is low" return while x != 0: hashval = (hashval << 3) + x%10 x /=10 return hashval % num def put(self, key, value): i = self.hash_fun(key,self.num) % self.num for p, (k, v) in enumerate(self.__solts__[i]): if k == key: break else: self.__solts__[i].append((key, value)) return self.__solts__[i][p] = (key, value) def get(self, key): i = self.hash_fun(key,self.num) % self.num for k, v in self.__solts__[i]: if k == key: return v raise KeyError(key) # keys函数 def keys(self): ret = [] for solt in self.__solts__: for k, _ in solt: ret.append(k) return ret def __getitem__(self,key): return self.get(key) def __setitem__(self,key,data): self.put(key,data) H = Dict(13) H[54] = "cat" H[26] = "dog" H[93] = "lion" H[17] = "tiger" H[77] = "bird" H[31] = "cow" H[44] = "goat" H[55] = "pig" H[20] = "chicken" print H.get(54) H.put(13,"duck") print H.__solts__ print H.keys()
运行结果:
cat [[], [], [(20, 'chicken')], [], [], [(17, 'tiger')], [(55, 'pig')], [(93, 'lion')], [], [], [(44, 'goat')], [(54, 'cat'), (26, 'dog'), (77, 'bird'), (31, 'cow')], [(13, 'duck')]] [20, 17, 55, 93, 44, 54, 26, 77, 31, 13]
参考文档:算法导论