献给cyt同学

#include <iostream>
#include <algorithm>
#include <map>
using namespace std;
map <int, int> h;
const int N = 2e5 + 10;
int n, m, x, a[N], ans;
int main(){

cin >> n >> m;
for (int i = 0; i < n; i ++ ){
	cin >> a[i];
	h[a[i]] ++;
} 
sort(a, a + n);
for (int i = 0; i < n; i ++ ){
	int l = 0, r = n - 1;
	int x = a[i] + m;
	while (l < r){
		int mid = (l + r) / 2;
		if(x <= a[mid]) r = mid;
		else l = mid + 1;
	}
	if(a[l] == x) ans += h[a[l]]; 
}
cout << ans << endl;
return 0;

}