hashmap 模板实现

来源：互联网发布：延长射精知乎编辑：程序博客网时间：2024/06/03 21:11

建立了一个hashmap类，该类的key必须大于0，用一个vector模拟hashmap.

写了build， insert 和delete 的函数。

目前，采用的是链式hash，就是相同的key的元素存放在一个数组中，目前用STL库中自带的vector类实现，以后，可以考虑用list实现。

代码如下：

// OOD.cpp : 定义控制台应用程序的入口点。//#include "stdafx.h"#include<iostream> #include<vector>using namespace std;/*implement the hash table using list*/template<typename T>struct hashelem{int key;vector<T> valuearray;hashelem(){key = -1;}};template<class T>class hashmap{public:hashmap();~hashmap();int cal_key_value(T elem); // calculate hash keyvector<hashelem<T>> buildhashtable(vector<T> elemarray);void hashinsert(T elem);void hashdelete(T elem);private:int capcity;int used;vector<hashelem<T>> hashelemarray;};template<class T>hashmap<T>::hashmap(){capcity = 20;used = 0;hashelemarray = vector<hashelem<T>>(capcity);}template<class T>hashmap<T>::~hashmap(){hashelemarray.clear();}template<class T>int hashmap<T>::cal_key_value(T elem){// here we use only a simple way to calculate hash keyint largenum = 5;return (elem%largenum);}template<class T>void hashmap<T>::hashinsert(T elem){if(used > 0.9 * capcity){cout<<"The hashtable is too crowded!!! Please rebuild hashtable!"<<endl;return;}int hashkey = cal_key_value(elem);hashelemarray[hashkey].valuearray.push_back(elem);hashelemarray[hashkey].key = hashkey;used++;}template<class T>void hashmap<T>::hashdelete(T elem){int hashkey = cal_key_value(elem);if(hashkey > hashelemarray.size()){cout << "ERROR:: NOT FIND"<<endl;return;}vector<T> tmparray = hashelemarray[hashkey].valuearray;int i;bool find = false;for(i = 0; i < tmparray.size();i++){if(tmparray[i] == elem){find = true;break;}}if(find){tmparray.erase(tmparray.begin()+i);if(tmparray.size() < 1){hashelemarray[hashkey].key = -1;hashelemarray[hashkey].valuearray = tmparray;}elsehashelemarray[hashkey].valuearray = tmparray;used--;}else{cout<<"ERROR: NO such element in hash table!"<<endl;return;}}template<class T>vector<hashelem<T>> hashmap<T>::buildhashtable(vector<T> elemarray){vector<hashelem<T>> result;if(elemarray.size() < 1)return result;for(int i =0; i < elemarray.size(); i++)hashinsert(elemarray[i]);return hashelemarray;}int main(){vector<int> V;hashmap<int> HM;for(int i = 0; i < 10; i++){V.push_back(rand()%100);}HM.buildhashtable(V);HM.hashdelete(V[3]);system("pause");return 0;}

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