哈希映射

#ifndef HASHMAP_H_
#define HASHMAP_H_

#include <vector>

template<class Key, class Value>
class HashMap  // 哈希映射 速度最快，
{
public:
HashMap(int size = 100) : 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;
else
return Value();
}
unsigned hash(const Key & k) const
{
unsigned int hashVal = 0;
const char *keyp = reinterpret_cast<const char *>(&k);  // 将k转变为字符，
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

#ifndef LINEARMAP_H_
#define LINEARMAP_H_

#include <vector>

template<class Key, class Value>
class LinearMap  // 线性映射  不使用，
{
public:
LinearMap(int size = 100) : arr(size)
{
currentSize = 0;
}
void Put(const Key & k,const Value & v)
{
arr[currentSize] = DataEntry(k,v);
++currentSize;
}
Value Get(const Key & k)  // 在这里可以看出它的查找速度非常的慢，
{
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

#include <iostream>
#include <map>  // 映射(也叫字典)，二叉树映射，不是哈希映射，
#include <hash_map> // 这个是C++自己做的哈希映射，是微软做的，
#include <string>
#include "LinearMap.h"
#include "HashMap.h"

using namespace std;

int main()
{
map<string,int> m; // 这是二叉树（红黑树）映射,
m["xiaocui"] = 88;
m["hengheng"] = 66;

cout << m["xiaocui"] << endl;

cout << "数组的优点： \n";
int a[100000];
for(int i = 0; i < 100000; ++i)
a[i] = i % 100;

cout << a[7] << endl;
cout << a[99912] << endl; // 数组的操作是对下标进行操作，速度非常的快，直接一下找到，

LinearMap<string,int> lm;
lm.Put("xiaocui",1314);

cout <<"LinerMap: " << lm.Get("xiaocui") << endl;

cout << "哈希映射：" << endl << endl;
HashMap<string,int> mymap;

cout << mymap.hash("xiaocui") << endl;
cout << mymap.myhash("xiaocui") << endl;
mymap.Put("xiaocui",9999);
mymap.Put("cuicui",88888);
cout << mymap.Get("cuicui") << endl;

cout << "使用C++自己做的哈希映射：" << endl;
hash_map<string,int> hm;
hm["xiao"] = 12;
hm["cui"] = 31;

cout << hm["cui"] << endl;

return 0;
}