数据结构-哈希与映射

二叉树映射map

#include<iostream>
#include<map>  //映射（也叫字典），二叉树映射，不是哈希映射
using namespace std;
int main()
{cout << "二叉树（红黑树）" << endl;map<string, int> m;m["bill"]= 67;m["toney"] = 98;m["Mary"] = 100;cout << m["Mary"] << endl;system("pause");return 0;
}

数组优点

#include<iostream>
#include<string>
using namespace std;
int main()
{//数组的优点//对下标（索引）进行非常快的地址运算//取arr[0]  arr[23232]  速度一样int arr[100000];int length = sizeof(arr) / sizeof(int);cout << length << endl;for (int i = 0; i < length; i++){arr[i] = i%100;}cout << arr[8] << endl;cout << arr[18] << endl;cout << arr[98756] << endl;system("pause");return 0;
}

线性映射

LinearMap.h

#ifndef LINEARMAP_H
#define LINEARMAP_H
#include<vector>
template<class Key,class Value>
class LinearMap  //线性映射-没用的东西
{
public:LinearMap(int size = 101) :arr(size){currentSize = 0;}void Put(const Key &k, const Value &v){arr[currentSize] = DataEntry(k, v);++currentSize;}Value Get(const Key & k){//线性查找for (size_t i = 0; i < currentSize; ++i){if (arr[i].key == k){return arr[i].value;}}return Value();}
private:struct DataEntry {Key key;Value value;DataEntry(const Key & k = Key(),const Value & v = Value()) : key(k), value(v) {}};std::vector<DataEntry> arr;int currentSize;
};#endif

linearMap.cpp

#include<iostream>
#include<string>
#include"LinearMap.h"
using namespace std;
int main()
{//没用的，仅学习的线性映射LinearMap<string, int> lm;lm.Put("bill", 99);lm.Put("Tom", 88);cout << "Lin  earMap:" << lm.Get("Tom") << endl;system("pause");return 0;
}

运行结果：

哈希映射

HashMap.h

#ifndef LINEARMAP_H
#define LINEARMAP_H
#include<vector>
template<class Key, class Value>
class HashMap  //哈希映射 最快
{
public:HashMap(int size = 101) :arr(size){currentSize = 0;}void Put(const Key &k, const Value &v){int pos = myHash(k);arr[pos] = DataEntry(k, v);++currentSize;}Value Get(const Key & k){int pos = myHash(k);if (arr[pos].key == k)return arr[pos].value;elsereturn Value();}unsigned hash(const Key & k) const{unsigned int hashVal = 0;const char* keyp = reinterpret_cast<const char*>(&k);  //转型for (size_t i = 0; i < sizeof(Key); i++){hashVal = 37 * hashVal + keyp[i];}return hashVal;}int myHash(const Key & k) const{unsigned hashVal = hash(k);hashVal %= arr.size();return hashVal;}private:struct DataEntry {Key key;Value value;DataEntry(const Key & k = Key(),const Value & v = Value()) : key(k), value(v) {}};std::vector<DataEntry> arr;int currentSize;
};#endif

HashMap.cpp

#include<iostream>
#include<string>
#include"HashMap.h"
using namespace std;
int main()
{HashMap<string, int> hm;/*cout << hm.hash("Bill") << endl;cout << hm.myHash("Bill") << endl;*/hm.Put("Bill", 33);hm.Put("Tom", 98);cout << hm.Get("Bill") << endl;//cout << hm.Get("Tom") << endl;  取两个就会错误system("pause");return 0;
}

运行结果：

c++自带的哈希映射(STL）

#define _SILENCE_STDEXT_HASH_DEPRECATION_WARNINGS
#include<iostream>
#include<string>
#include<hash_map>
using namespace std;
//使用C++封装好的hash_map
//又要排序又要映射时就用tree_map(二叉树映射)
int main()
{hash_map<string, int> hm;hm["Bill"] = 12;hm["Tom"] = 22;hm["Mary"] = 34;cout << hm["Mary"] << endl;cout << hm["Tom"] << endl;system("pause");return 0;
}

运行结果：