哈希衝突之散列法

哈希碰撞/哈希衝突：不同的Key值經過哈希函數Hash(Key)處理以後可能產生相同的值哈希地址，我們稱這種情況爲哈希衝突。任意的散列函數都不能避免產生衝突。

#include<iostream>
#include<vector>
using namespace std;
enum State
{
	EMPTY,
	DELETE,
	EXIST,
};
class HashTable
{
public:
	HashTable(int capacity)
	{
		v.reserve(capacity);
		v.assign(capacity, 0);
		s.reserve(capacity);
		s.assign(capacity, EMPTY);
		_size = 0;
	}
	//閉散列法——線性探測
	void Insert1(int x)
	{
		int pos = x % v.capacity();
		while (s[pos] == EXIST)
		{
			if (v[pos] == x)
			{
				return;
			}
			pos++;
			if (pos == v.capacity())
			{
				pos = 0;
			}
		}
		s[pos] = EXIST;
		v[pos] = x;
		++_size;
	}

	//閉散列法——二次探測
	int Curpos(int Lastpos, int i,int capacity)
	{
		return (Lastpos + 2 * i - 1) % capacity;
	}


	void Insert2(int x)
	{
		_CreatExpand();
		int i = 0;
		int pos = x%v.capacity();
		while (s[pos] == EXIST)
		{
			if (v[pos] == x)
			{
				return;
			}
			pos = Curpos(pos, ++i,v.capacity());
		}
		s[pos] = EXIST;
		v[pos] = x;
		++_size;
	}
	void Print()
	{
		for (int i = 0; i < v.capacity(); i++)
		{
			printf("【%d, %d】\t", v[i], s[i]);
		}
		cout << endl;
	}
protected:
	void _CreatExpand()
	{
		if (_size >= (int)(v.capacity()*0.7))
		{
			vector<int>v1;
			v1.reserve(2 * v.capacity());
			v1.assign(v1.capacity(), 0);
			vector<State>s1;
			s1.reserve(2 * s.capacity());
			s1.assign(s1.capacity(), EMPTY);

			for (int i = 0; i < (int)v.capacity(); i++)
			{
				if (s[i] == EXIST)
				{
					int k = 0;//第幾次哈希衝突
					int pos = v[i] % v1.capacity();
					while (s1[pos] == EXIST)
					{
						pos = Curpos(pos, ++k, v1.capacity());
					}
					s1[pos] = EXIST;
					v1[pos] = v[i];
				}
			}
			v.swap(v1);
			s.swap(s1);
			_size = v.size();
		}
	}
private:
	vector<int>v;
	vector<State>s;
	int _size;
};</span>