hashtable的C++实现

#include <vector>
#include <list>
using namespace std;

template <typename HashedObj>
class HashTable
{
public:
explicit HashTable(int size = 101);

void makeEmpty()
{
for(int i = 0; i < theLists.size(); i++)
theLists[i].clear();
}

bool contains(const HashedObj & x) const
{
const list<HashedObj> & whichList = theLists[myhash(x)];
return find(whichList.begin(), whichList.end(), x) != whichList.end();
}

bool remove(const HashedObj & x)
{
list<HashedObj> & whichList = theLists[myhash(x)];
typename list<HashedObj>::iterator itr = find(whichList.begin(), whichList.end(), x);
if(itr == whichList.end())
return false;
whichList.erase(itr);
--currentSize;
return true;
}

bool insert(const HashedObj & x)
{
list<HashedObj> & whichList = theLists[myhash(x)];
if(find(whichList.begin(), whichList.end(), x) != whichList.end())
return false;
whichList.push_back(x);
if(++currentSize > theLists.size())
rehash();
return true;
}

private:
vector<list<HashedObj> > theLists;   // The array of Lists
int  currentSize;

void rehash()
{
vector<list<HashedObj> > oldLists = theLists;

// Create new double-sized, empty table
theLists.resize(2 * theLists.size());
for(int j = 0; j < theLists.size(); j++)
theLists[j].clear();

// Copy table over
currentSize = 0;
for(int i = 0; i < oldLists.size(); i++)
{
typename list<HashedObj>::iterator itr = oldLists[i].begin();
while(itr != oldLists[i].end())
insert(*itr++);
}
}

int myhash(const HashedObj & x) const
{
int hashVal = hash(x);

hashVal %= theLists.size();
if(hashVal < 0)
hashVal += theLists.size();

return hashVal;
}
};