Submission #780484

#	Time	Username	Problem	Language	Result	Execution time	Memory
780484		quochuy147	Museum (CEOI17_museum)	C++14	100 / 100	260 ms	140424 KiB

museum

#include <bits/stdc++.h>
 
using namespace std;
 
#define fi first
#define se second
#define ll long long
#define mp make_pair
#define pb push_back
#define pii pair<int, int>
#define pll pair<ll, ll>
#define MASK(i) (1LL << (i))
#define BIT(x, i) (((x) >> (i)) & 1)
#define TIME  (1.0 * clock() / CLOCKS_PER_SEC)
#define file "name" 
template <typename T1, typename T2> bool minimize(T1 &a, T2 b){if (a > b) {a = b; return true;} return false;}
template <typename T1, typename T2> bool maximize(T1 &a, T2 b){if (a < b) {a = b; return true;} return false;}
 
const int mod = 1e9 + 7;
const int N = 1e4 + 2;
const int inf = 1e9;
 
int n, k, x;
int sz[N];
vector <int> f[N][2];
vector <pii> a[N];
 
void inp()
{
    cin >> n >> k >> x;
    for(int i = 1; i < n; ++i) {
        int u, v, w;
        cin >> u >> v >> w;
        a[u].pb({v, w});
        a[v].pb({u, w});
    }
}
 
void size_subtree(int u, int pre) {
    sz[u] = 1;
    for(auto v : a[u]) {
        if(v.fi == pre) continue;
        size_subtree(v.fi, u);
        sz[u] += sz[v.fi];
    }
}
 
void dfs(int u, int pre) {
    f[u][0].assign(min(k, sz[u]) + 2, inf);
    f[u][1].assign(min(k, sz[u]) + 2, inf);
    f[u][0][0] = f[u][0][1] = f[u][1][0] = f[u][1][1] = 0;
    int tot = 1;
    for(auto e : a[u]) {
        int v = e.fi, w = e.se;
        if(v == pre) continue;
        dfs(v, u);
        tot += sz[v];
        for(int i = tot; i >= 2; --i) {
            if(i > k) continue;
            for(int j = max(0, i - tot + sz[v]); j <= min(i, sz[v]); ++j) {
                minimize(f[u][0][i], f[u][0][i - j] + f[v][1][j] + 2 * w);
                minimize(f[u][0][i], f[u][1][i - j] + f[v][0][j] + w);
                minimize(f[u][1][i], f[u][1][i - j] + f[v][1][j] + 2 * w);
            }
        }
    }
}
 
void solve()
{
    size_subtree(x, x);
    dfs(x, x);
    cout << f[x][0][k];
}
 
int main()
{
    cin.tie(0)->sync_with_stdio(0);
    // freopen(file".inp" , "r" , stdin);
    // freopen(file".out" , "w" , stdout);
    inp();
    solve();
    return 0;
}

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