https://www.acwing.com/blog/content/30297/
主要是明白第一位一定存在

#include <bits/stdc++.h>
using namespace std;
// 1 2 4 5 7 8
int main() {
    int n, d;
    cin >> n >> d;
    vector<int> nums(n, 0);
    for(int i = 0; i < n; i ++) cin >> nums[i];
    sort(nums.begin(), nums.end());

    int cnt = 1;
    int last = nums[0];
    for(int i = 1; i < n; i ++) {
        int nd = nums[i] - last;
        if(nd < d) continue;
        cnt ++;
        last = nums[i];
    }
    cout << cnt;
    return 0;
}