Submission #537282

#	Time	Username	Problem	Language	Result	Execution time	Memory
537282		Lobo	Beads and wires (APIO14_beads)	C++17	0 / 100	3 ms	5460 KiB

beads

#include<bits/stdc++.h>
using namespace std;
 
const long long inf = (long long) 1e15 + 10;
const int inf1 = (int) 1e9 + 10;
#define int long long
#define dbl long double
#define endl '\n'
#define sc second
#define fr first
#define mp make_pair
#define pb push_back
#define all(x) x.begin(), x.end()
 
#define maxn 220000
 
int n, dp[maxn][5], mark[maxn][5], a[maxn], b[maxn], c[maxn];
vector<pair<int,int>> g[maxn];
 
int sol(int u, int p, int ant) {
    if(mark[u][p]) return dp[u][p];
    mark[u][p] = 1;
 
    if(p == 0) {
        //o pai liga para ele, entao pode ligar para 2 com 
        //aresta azul, para 1 com aresta vermelha ou para nenhum
 
        int ans = 0;
        //dois filhos
        //liga para 2 com aresta azul
        ans = 0;
        pair<int,int> mx2 = mp(-inf,-inf);
        for(auto V : g[u]) {
            int v = V.fr;
            int w = V.sc;
            if(v == ant) continue;
            ans+= max(sol(v,1,u),sol(v,3,u)+w);
            mx2.sc = max(mx2.sc, w + sol(v,0,u) - max(sol(v,1,u),sol(v,3,u)+w));
            if(mx2.sc > mx2.fr) swap(mx2.sc,mx2.fr);
        }
 
        int ans2 = ans+mx2.fr+mx2.sc;
 
        //liga para nenhum/todos ligam para ele
        //ele pode ajudar exatamente um filho a ser sol(v,2,u)
        ans = 0;
        int mx0 = -inf;
        for(auto V : g[u]) {
            int v = V.fr;
            int w = V.sc;
            if(v == ant) continue;
            ans+= max(sol(v,1,u),sol(v,3,u)+w);
            mx0 = max(mx0, sol(v,2,u)+w - max(sol(v,1,u),sol(v,3,u)+w));
        }
 
        int ans0 = ans+mx0;
 
        //liga para 1 com aresta vermelha
        int mx1 = -inf;
        ans = 0;
        for(auto V : g[u]) {
            int v = V.fr;
            int w = V.sc;
            if(v == ant) continue;
            ans+= max(sol(v,1,u),sol(v,3,u)+w);
            mx1 = max(mx1, sol(v,0,u) - max(sol(v,1,u),sol(v,3,u)+w));
        }
        int ans1 = ans+mx1;
 
        // cout << u << " " << p << " = " << max({ans0,ans1,ans2}) << endl;
        return dp[u][p] = max({ans0,ans1,ans2});
    }
    else if(p == 1) {
        //p = 1, liga dele pro pai com red
        int ans = 0;
        //liga para nenhum/todos ligam para ele
        //ele pode ajudar exatamente um filho a ser sol(v,2,u)
        ans = 0;
        int mx0 = -inf;
        for(auto V : g[u]) {
            int v = V.fr;
            int w = V.sc;
            if(v == ant) continue;
            ans+= max(sol(v,1,u),sol(v,3,u)+w);
            mx0 = max(mx0, sol(v,2,u)+w - max(sol(v,1,u),sol(v,3,u)+w));
        }
 
        int ans0 = ans+mx0;
        // cout << u << " " << p << " = " << ans0 << endl;
        return dp[u][p] = ans0;
    }
    else if(p == 2) {
        //o pai ja ligou para ele
        int mx = -inf;
        int ans = 0;
        for(auto V : g[u]) {
            int v = V.fr;
            int w = V.sc;
            if(v == ant) continue;
 
            ans+= max(sol(v,1,u),sol(v,3,u)+w);
            mx = max(mx, w +sol(v,0,u) - max(sol(v,1,u),sol(v,3,u)+w));
        }
 
        // cout << u << " " << p << " = " << ans+mx << endl;
        return dp[u][p] = ans+mx;
    }
    else if(p == 3) {
        //o v especial vai ter que ligar pro pai
        int mx = -inf;
        int ans = 0;
        for(auto V : g[u]) {
            int v = V.fr;
            int w = V.sc;
            if(v == ant) continue;
 
            ans+= max(sol(v,1,u),sol(v,3,u)+w);
            mx = max(mx, w + sol(v,1,u) - max(sol(v,1,u),sol(v,3,u)+w));
        }
 
        // cout << u << " " << p << " = " << ans+mx << endl;
        return dp[u][p] = ans+mx;
    }
    return 0;
}
 
void solve() {
    cin >> n;
 
    for(int i = 1; i < n; i++) {
        cin >> a[i] >> b[i] >> c[i];
        g[a[i]].pb(mp(b[i],c[i]));
        g[b[i]].pb(mp(a[i],c[i]));
    }
 
    int rt;
    for(int i = 1; i <= n; i++) {
        if(g[i].size() == 1) {
            rt = i;
            break;
        }
    }
 
 
    cout << sol(rt,0,0) << endl;
 
}
 
int32_t main() {
    ios::sync_with_stdio(false); cin.tie(0);
 
    // freopen("in.in", "r", stdin);
    // freopen("out.out", "w", stdout);
 
    int tt = 1;
    // cin >> tt;
    while(tt--) solve();
 
}

Compilation message (stderr)

beads.cpp: In function 'void solve()':
beads.cpp:136:9: warning: 'rt' may be used uninitialized in this function [-Wmaybe-uninitialized]
  136 |     int rt;
      |         ^~

• Subtask 1: 0 / 13
• Subtask 2: 0 / 15
• Subtask 3: 0 / 29
• Subtask 4: 0 / 43