How can I improve memory usage in this code?

#include "bits/stdc++.h"

using namespace std;

int main() {
    cin.tie(nullptr)->sync_with_stdio(false);
    short n;
    cin >> n;

    vector<pair<int,short>> s(n, pair<int,int>());

    for (int i = 0; i < n; i ++) {
        cin >> s[i].first;
        s[i].second = i;
    }

    sort(begin(s),end(s));
    for (short i = 1; i < n; i ++) {
        if (s[i].first == s[i - 1].first) {
            s.erase(begin(s) + i);
            n --;
            i --;
        }
    }

    vector<vector<short>> dp(n + 1, vector<short>(n + 1, 0));

    for (short i = 1; i < n - 1; i ++) {
        short l = i - 1;
        short r = i + 1;
        while (0 <= l && r < n) {
            int dfl = s[i].first - s[l].first;
            int dfr = s[r].first - s[i].first;
            if (dfl == dfr) {
                dp[i][r] = dp[l][i] + 1;
                l --;
                r ++;
            } else if (dfl > dfr) {
                r ++;
            } else {
                l --;
            }
        }
    }

    if (1 == n) {
        cout << "1\n1\n";
    } else {
        short mx = -1;
        short di = 0;
        short dj = 0;

        for (int i = 0; i < n - 1; i ++) {
            for (int j = i + 1; j < n; j ++) {
                if (dp[i][j] >= mx) {
                    mx = dp[i][j];
                    di = i;
                    dj = j;
                }
            }
        }

        int df = s[dj].first - s[di].first;

        mx += 2;

        cout << mx << '\n';

        for (; -1 < di;) {
            cout << s[dj].second + 1 << ' ';
            dj = di;
            di = -1;
            for (short i = 0; i < dj; i ++) {
                if (s[dj].first - s[i].first == df) {
                    di = i;
                    break;
                }
            }
        }

        cout << s[dj].second + 1 << '\n';
    }
}

Don't use std::vector at all. Especially for 2D arrays. Vector can be twice more than you suppose )