Submission #955808

#	Time	Username	Problem	Language	Result	Execution time	Memory
955808		vjudge1	Sparklers (JOI17_sparklers)	C++17	50 / 100	150 ms	262144 KiB

sparklers

#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
int main()
{
    ios::sync_with_stdio(0);
    cin.tie(0);
    ll n, k, t, i, j, a, lo = 1, hi = (1 << 30), s;
    cin >> n >> k >> t;
    k--;
    vector<ll> v(n);
    for (i = 0; i < n; i++)
        cin >> v[i];
    if (!v[n - 1])
    {
        cout << 0;
        return 0;
    }
    vector<vector<bool> > dp(n);
    queue<vector<ll> > q;
    for (i = 0; i < n; i++)
        dp[i].resize(i + 1);
    while (hi - lo > 1)
    {
        s = (hi + lo) / 2;
        for (i = 0; i < n; i++)
        {
            for (j = 0; j <= i; j++)
                dp[i][j] = 0;
        }
        dp[k][k] = 1;
        q.push({k, k});
        while (!q.empty())
        {
            i = q.front()[0];
            j = q.front()[1];
            q.pop();
            a = 2 * t * s * (i - j + 1);
            if (j && !dp[i][j - 1] && v[i] - v[j - 1] <= a)
            {
                dp[i][j - 1] = 1;
                q.push({i, j - 1});
            }
            if (i < n - 1 && !dp[i + 1][j] && v[i + 1] - v[j] <= a)
            {
                dp[i + 1][j] = 1;
                q.push({i + 1, j});
            }
        }
        if (dp[n - 1][0])
            hi = s;
        else
            lo = s;
    }
    cout << hi;
    return 0;
}

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