codeforces 251A Points on Line 二分 or 单调队列

#include<cstdio>
#include<cstring>
#include<algorithm>
using namespace std;
#define LL __int64
int d, n;
int a[100005];
LL ans;
int main()
{
int i, j;
scanf("%d%d", &n, &d);
for(i = 0; i < n; i++)
scanf("%d", &a[i]);
for(i = 1; i < n; i++)
j = i - (lower_bound(a, a+i, a[i] - d) - a),
ans += (LL)j *(j-1)/2;
printf("%I64d\n", ans);
return 0;
}