Submission #1197388

#	Time	Username	Problem	Language	Result	Execution time	Memory
1197388		og_matveychick1	Sparklers (JOI17_sparklers)	C++20	50 / 100	160 ms	16260 KiB

sparklers

#include "bits/stdc++.h"

using namespace std;

typedef long long ll;
typedef pair<ll, ll> pll;

const ll N = 1e3 + 5;

ll n, k, t, a[N];
pair<ll, ll> dp[N][N];

void update(ll l, ll r, pll x, pll y) {
    pll b = {max(x.first, y.first), min(x.second, y.second)};
    if (b.first > b.second) return;
    if (dp[l][r].first < b.first) return;
    dp[l][r].first = min(dp[l][r].first, b.first);
    dp[l][r].second = max(dp[l][r].second, b.second);
}

bool check(ll s) {
    if (s * t > 1e9) return 1;
    for (ll i = 0; i < N; i++) for (ll j = 0; j < N; j++) dp[i][j] = {1e18, -1e18};
    dp[k][k] = {a[k], a[k]};
    for (ll d = 1; d < n; d++) {
        for (ll l = 0, r = l + d - 1; r < n; l++, r++) {
            if (r != n - 1) {
                update(l, r + 1, {dp[l][r].first - t * s, dp[l][r].second + t * s},
                       {a[r + 1] - d * t * s, a[r + 1] + d * t * s});
            }
            if (l - 1 != -1) {
                update(l - 1, r, {dp[l][r].first - t * s, dp[l][r].second + t * s},
                       {a[l - 1] - d * t * s, a[l - 1] + d * t * s});
            }

        }
    }
    return dp[0][n - 1].second - dp[0][n - 1].first >= 0;
}

signed main() {
    ios::sync_with_stdio(0), cin.tie(0), cout.tie(0);
    cin >> n >> k >> t, k--;
    for (ll i = 0; i < n; i++) cin >> a[i];
    ll l = -1, r = 1e9 / t + 5;
    check(38);
    while (l + 1 < r) {
        ll m = (l + r) / 2;
        (check(m) ? r : l) = m;
    }
    cout << r;
}

• Subtask 1: 30 / 30
• Subtask 2: 20 / 20
• Subtask 3: 0 / 50