Grupe X - 6.6.1 / pag 171

#include <bits/stdc++.h>

using namespace std;

inline void max_self(int& a, int b) {
    a = max(a, b);
}

int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);
    cout.tie(nullptr);
    int N, x;
    cin >> N >> x;
    vector < int > a(N);
    for(int& x : a)
        cin >> x;
    vector < int > dp(N);
    dp[N - 1] = 1;
    int ans = 1;
    for(int i = N - 2; i >= 0; --i) {
        int mx = 0;
        for(int j = i + 1; j < N; ++j)
            if(a[j] - a[i] >= x)
                max_self(mx, dp[j]);
        dp[i] = mx + 1;
        max_self(ans, dp[i]);
    }
    cout << ans;
}