算法导论11.2散列表Hash tables链式法解决碰撞11.3.1除法散列法
11.2是第11章的主要内容,11章叫散列表(Hash Tables)11.2也叫散列表(Hash Tables)
11.3节讲散列函数(比如除尘散列法),11.4节讲处理碰撞的另外一种方法区别于链式法技术
散列技术,有两个事情要做,一是先哈希函数(11.3),二是解决碰撞技术(11.2链式解决碰撞,11.4开放寻址解决碰撞)。
/* * IA_11.2ChainedHash.h * * Created on: Feb 13, 2015 * Author: sunyj */ #ifndef IA_11_2CHAINEDHASH_H_ #define IA_11_2CHAINEDHASH_H_ #include <iostream> #include <string.h> #include "IA_10.2LinkedLists.h" // CHAINED-HASH-INSERT(T, x) // insert x at the head of list T[h(x.key)] // CHAINED-HASH-SEARCH(T, k) // search for an element with key k in list T[h(k)] // CHAINED-HASH-DELETE(T, x) // delete x from the list T[h(x.key)] template <class T> class ChainedHashTable { public: ChainedHashTable(int64_t const n) : size(n) { data = new LinkedList<int64_t, T>[n](); } ~ChainedHashTable() {} int64_t HashFunc(int64_t const key) { return key % size; } Node<int64_t, T>* search(int64_t const key) { return data[HashFunc(key)].search(key); } // the user of this class, has to invoke search first // this interface assume that x was not in the hash table void insert(Node<int64_t, T>* x) { (data[HashFunc(x->key)]).insert(x); } void del(Node<int64_t, T>* x) { data[HashFunc(x->key)].del(x); } void print(int64_t key) { data[HashFunc(key)].print(); } private: LinkedList<int64_t, T>* data; int64_t const size; }; #endif /* IA_11_2CHAINEDHASH_H_ */
/* * IA_11.2ChainedHash.cpp * * Created on: Feb 12, 2015 * Author: sunyj */ #include "IA_11.2ChainedHash.h" int main() { /* * A prime not too close to an exact power of 2 is often a good choice for m. For example, suppose we wish to allocate a hash table, with collisions resolved by chaining, to hold roughly n = 2000 character strings, where a character has 8 bits. We don't mind examining an average of 3 elements in an unsuccessful search, and so we allocate a hash table of size m = 701. We could choose 701 because it is a prime near 2000=3 but not near any power of 2. */ ChainedHashTable<int64_t> table(701); // The division method, Node<int64_t, int64_t> node1(1, 100); Node<int64_t, int64_t> node4(4, 400); Node<int64_t, int64_t> node16(16, 1600); Node<int64_t, int64_t> node9(9, 900); if (nullptr == table.search(node1.key)) { // search before insert table.insert(&node1); } else { std::cout << "node1 already exist" << std::endl; } if (nullptr == table.search(node1.key)) { table.insert(&node1); } else { std::cout << "node1 already exist" << std::endl; } table.insert(&node4); table.insert(&node16); table.insert(&node9); table.print(4); Node<int64_t, int64_t> node25(25, 2500); table.insert(&node25); table.print(16); // search before del, or you are clearly sure that, there are this node exist. // if node1 is not exist, and you invoke del, program will crush table.del(&node1); table.print(9); Node<int64_t, int64_t>* tmp; tmp = table.search(9); table.del(tmp); table.print(9); return 0; }