Submission #1125857

#	Time	Username	Problem	Language	Result	Execution time	Memory
1125857		tgh317127	Museum (CEOI17_museum)	C++20	20 / 100	773 ms	1114112 KiB

museum

#include<bits/stdc++.h>
#define ll long long
#define ld long double
#define pii pair<int, int>
#define pll pair<ll, ll>
#define MASK(i) ((1LL) << (i))
#define BIT(x, i) (((x) >> (i)) & 1)
#define fi first
#define se second

using namespace std;

const long inf = 1e9 + 7;
const long mod = 1e9 + 7;
const long Nmax = 1e4 + 7;
const long lg = 20;
const long bs = 1003;

int n, k, x;
vector<pii> g[Nmax];
pll dp[Nmax][Nmax];
pll pref[Nmax];
int sz[Nmax];

void combine(int u, int v, int c)
{
    for (int i = 1; i <= sz[u]; i++)
    {
        for (int j = 1; j <= sz[v]; j++)
        {
            if (i + j > sz[u]) break;
            pll val = pref[i];
            val.fi += dp[v][j].fi + 2 * c;
            val.se = max(val.se, dp[v][j].se + c);
//            cerr << val.fi << " " << val.se << "\n";
            if (dp[u][i + j].fi - dp[u][i + j].se > val.fi - val.se) dp[u][i + j] = val;
            else if (dp[u][i + j].fi - dp[u][i + j].se == val.fi - val.se)
            {
                if (dp[u][i + j].fi > val.fi) dp[u][i + j] = val;
            }
        }
    }
    for (int i = 1; i <= sz[u]; i++)
    {
        if (pref[i].fi - pref[i].se > dp[u][i].fi - dp[u][i].se) pref[i] = dp[u][i];
//        cerr << dp[u][i].fi << " " << dp[u][i].se << "\n";
    }
}

void dfs(int u, int p)
{
    sz[u] = 1;
    for (auto v : g[u])
    {
        if (v.fi == p) continue;
        dfs(v.fi, u);
        sz[u] += sz[v.fi];
    }
    for (int i = 0; i <= sz[u]; i++) pref[i] = {1LL * inf * inf, -1LL * inf * inf};
    pref[1] = {0, 0};
    for (auto v : g[u])
    {
        if (v.fi == p) continue;
        combine(u, v.fi, v.se);
    }
    dp[u][0] = {0, 0};
    dp[u][1] = {0, 0};
}

int main()
{
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    //freopen("name.inp","r",stdin);
    //freopen("name.out","w",stdout);
    cin >> n >> k >> x;
    for (int i = 1; i < n; i++)
    {
        int u, v, c;
        cin >> u >> v >> c;
        g[u].push_back({v, c});
        g[v].push_back({u, c});
    }

    for (int i = 1; i <= n; i++)
        for (int j = 1; j <= n; j++)
            dp[i][j] = {1LL * inf * inf, -1LL * inf * inf};

    dfs(x, -1);
//    for (int i = 0; i <= 10; i++) cerr << dp[7][i].fi << " " << dp[7][i].se << "\n";
//    ll res = 8 * 1LL * inf * inf;
//    for (int i = 1; i <= n; i++)
//    {
//        res = min(res, dp[i][k].fi - dp[i][k].se);
////        cerr << dp[i][k].fi << " " << dp[i][k].se << "\n";
//    }
//    cout << res << "\n";
    cout << dp[x][k].fi - dp[x][k].se << "\n";
}

• Subtask 1: 20 / 20
• Subtask 2: 0 / 25
• Subtask 3: 0 / 35
• Subtask 4: 0 / 20