题解

#include <iostream>
#include <algorithm>
using namespace std;
int n,a[200010],sum,c;
int main()
{
cin>>n>>c;
for(int i=1;i<=n;i++)
cin>>a[i];
sort(a+1 ,a+n+1);
for(int i=1;i<=n;i++)
{
int b=a[i]-c;
int pos2=upper_bound(a+1,a+n+1,b)-a;
int pos1=lower_bound(a+1,a+n+1, b)-a;
sum+=pos2-pos1;
}
cout<<sum;
return 0;
}