RT 手打 hash map WA#3

#include<iostream>
using namespace std;
int n, m;
template<typename Ta, typename Tb>
class map
{
public:
	struct value;
private:
	int _size;
	struct node
	{
		Ta pos;
		value val;
		node* next;
	};
	struct head
	{
		node* lead = nullptr;
	};
	head* h;
	const unsigned _hash(Ta ta) { return (unsigned)ta; }
public:
	struct value
	{
		Tb val;
		value* from;
		void root()
		{
			if (from->from == from)
				return;
			from->root();
			val = from->val;
			from = from->from;
		}
		operator Tb() const
		{
			return val;
		}
		void operator = (Tb tb)
		{
			root();
			from->val = tb;
		}
		value()
		{
			from = this;
		}
		value(Tb tb) :val(tb)
		{
			val = tb;
			from = this;
		}
	};
	map()
	{
		h = new head[_size];
	}
	map(unsigned size = 0x10000)
	{
		_size = size;
		h = new head[_size];
	}
	value at(Ta pos)
	{
		int p = _hash(pos) % _size;
		for (node* i = h[p].lead; i != nullptr; i = i->next)
		{
			if (i->pos == pos)
				return i->val;
		}
		node* nw; nw = new node;
		nw->next = h[p].lead;
		h[p].lead = nw;
		nw->pos = pos;
		nw->val = NULL;
		return nw->val;
	}
	value operator [] (Ta pos)
	{
		return at(pos);
	}
	value operator + (Ta pos)
	{
		return at(pos);
	}
};
map<int, int> mp(1000000);
int main()
{
	int n, c, a, ans=0;
	cin >> n >> c;
	for (int i = 1; i <= n; i++)
	{
		cin >> a;
		ans += mp[a - c];
		ans += mp[a + c];
		mp[a]=mp[a]+1;
	}
	cout << ans;
}