Submission #1066142

#	Time	Username	Problem	Language	Result	Execution time	Memory
1066142		_callmelucian	Chase (CEOI17_chase)	C++14	100 / 100	2731 ms	39064 KiB

chase

#include <bits/stdc++.h>
using namespace std;

typedef long long ll;
typedef long double ld;
typedef pair<ll,ll> pl;
typedef pair<int,int> pii;
typedef tuple<int,int,int> tt;

#define all(a) a.begin(), a.end()
#define filter(a) a.erase(unique(all(a)), a.end())

const int mn = 1e5 + 5;
ll pigeon[mn], neighbour[mn], dpDown[2][2][mn], dpUp[2][2][mn], dpExcept[2][2][mn];
vector<int> adj[mn];

struct helper {
    vector<ll> pre, sfx;
    int n;

    helper (vector<ll> a) : pre(a.size()), sfx(a.size()), n(a.size()) {
        if (!n) return;
        pre[0] = a[0], sfx[n - 1] = a[n - 1];
        for (int i = 1; i < n; i++)
            pre[i] = max(pre[i - 1], a[i]);
        for (int i = n - 2; i >= 0; i--)
            sfx[i] = max(sfx[i + 1], a[i]);
    }

    ll getPre (int p) {
        return (0 <= p && p < n ? pre[p] : 0);
    }

    ll getSfx (int p) {
        return (0 <= p && p < n ? sfx[p] : 0);
    }

    ll query (int exc = -1) {
        if (exc == -1) return getPre(n - 1);
        return max(getPre(exc - 1), getSfx(exc + 1));
    }
};

void dfsDown (int u, int p, int bread) {
    int t = bread & 1;

    vector<ll> v1(adj[u].size()), v2(adj[u].size());
    for (int i = 0; i < adj[u].size(); i++) {
        int v = adj[u][i]; if (v == p) continue;
        dfsDown(v, u, bread);
        v1[i] = max(dpDown[t ^ 1][1][v] - pigeon[u], dpDown[t ^ 1][0][v]);
        v2[i] = max(dpDown[t][1][v] - pigeon[u], dpDown[t][0][v]);
    }
    helper take(v1), ignore(v2);

    dpDown[t][1][u] = take.query() + neighbour[u];
    dpDown[t][0][u] = ignore.query();
    for (int i = 0; i < adj[u].size(); i++) {
        int v = adj[u][i]; if (v == p) continue;
        dpExcept[t][1][v] = take.query(i) + neighbour[u];
        dpExcept[t][0][v] = ignore.query(i);
    }
}

void dfsUp (int u, int p, int bread) {
    int t = bread & 1;
    dpUp[t][1][u] = neighbour[u];
    if (u != p) {
        ll take = max({dpUp[t ^ 1][1][p] - pigeon[u], dpUp[t ^ 1][0][p], dpExcept[t ^ 1][1][u] - pigeon[u], dpExcept[t ^ 1][0][u]});
        ll ignore = max({dpUp[t][1][p] - pigeon[u], dpUp[t][0][p], dpExcept[t][1][u] - pigeon[u], dpExcept[t][0][u]});
        dpUp[t][1][u] = take + neighbour[u], dpUp[t][0][u] = ignore;
    }

    for (int v : adj[u])
        if (v != p) dfsUp(v, u, bread);
}

int main()
{
    ios::sync_with_stdio(0);
    cin.tie(0);

    int n, v; cin >> n >> v;
    for (int i = 1; i <= n; i++) cin >> pigeon[i];
    for (int i = 1; i < n; i++) {
        int a, b; cin >> a >> b;
        neighbour[a] += pigeon[b];
        neighbour[b] += pigeon[a];
        adj[a].push_back(b);
        adj[b].push_back(a);
    }

    if (v == 0) return cout << 0, 0;

    for (int i = 1; i <= v; i++) {
        dfsDown(1, 1, i);
        dfsUp(1, 1, i);
    }

    ll ans = 0;
    for (int i = 1; i <= n; i++)
        ans = max({ans, dpDown[v & 1][1][i], dpUp[v & 1][1][i]});
    cout << ans;

    return 0;
}

Compilation message (stderr)

chase.cpp: In function 'void dfsDown(int, int, int)':
chase.cpp:48:23: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   48 |     for (int i = 0; i < adj[u].size(); i++) {
      |                     ~~^~~~~~~~~~~~~~~
chase.cpp:58:23: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   58 |     for (int i = 0; i < adj[u].size(); i++) {
      |                     ~~^~~~~~~~~~~~~~~

• Subtask 1: 20 / 20
• Subtask 2: 20 / 20
• Subtask 3: 30 / 30
• Subtask 4: 30 / 30