Submission #520406

#	Time	Username	Problem	Language	Result	Execution time	Memory
520406		TAMREF	Beads and wires (APIO14_beads)	C++17	0 / 100	3 ms	4940 KiB

beads

#include <bits/stdc++.h>
#define va first
#define vb second
#define lb lower_bound
#define ub upper_bound
#define bs binary_search
#define pp push_back
#define ep emplace_back
#define all(v) (v).begin(),(v).end()
#define szz(v) ((int)(v).size())
#define bi_pc __builtin_popcount
#define bi_pcll __builtin_popcountll
#define bi_tz __builtin_ctz
#define bi_tzll __builtin_ctzll
#define fio ios_base::sync_with_stdio(0);cin.tie(0);
#ifdef TAMREF
#define debug(...) fprintf(stderr, __VA_ARGS__)
#else
#define debug(...) 42
#endif
using namespace std;
using ll = long long; using lf = long double; 
using pii = pair<int,int>; using ppi = pair<int,pii>;
using pll = pair<ll,ll>; using pff = pair<lf,lf>;
using ti = tuple<int,int,int>;
using base = complex<double>;
const lf PI = 3.14159265358979323846264338L;
template <typename T>
inline T umax(T& u, T v){return u = max(u, v);}
template <typename T>
inline T umin(T& u, T v){return u = min(u, v);}
mt19937_64 rng(chrono::steady_clock::now().time_since_epoch().count());

const int mx = 2e5 + 5;
ll up[mx], dp[mx];
vector<pii> G[mx];
int vis[mx];
int n;

ll dfs(int x) {
    // debug("dfs %d, vis = %d\n", x, vis[x]);
    set<pll> pq;
    up[x] = -1e5;
    dp[x] = 0;
    ll sum = 0;
    for(auto [u, w] : G[x]) {
        // debug("u = %d with vis = %d\n", u, vis[u]);
        if(vis[u] == vis[x]) continue;
        vis[u] = vis[x];
        dfs(u);
        sum += max(up[u] + w, dp[u]);
        debug("x = %d, u = %d, sum = %lld\n", x, u, sum);
        pq.emplace(min(dp[u] - up[u], ll(w)), u);
        while(szz(pq) > 2) pq.erase(pq.begin());
    }
    if(szz(pq)) {
        up[x] = sum + pq.rbegin() -> va;
        dp[x] = sum;
    }
    if(szz(pq) > 1) {
        auto [w1, u1] = *pq.rbegin();
        auto [w2, u2] = *next(pq.rbegin());
        debug("got alternator (%lld, %lld) and (%lld, %lld)\n", w1, u1, w2, u2);
        dp[x] = max(sum, sum + w1 + w2);
    }
    debug("up[%d] = %lld, dp[%d] = %lld\n", x, up[x], x, dp[x]);
    return sum;
}

int main(){
    fio;
    cin >> n;
    if(n == 1) {
        cout << 0 << endl;
        return 0;
    }
    for(int i = 1, a, b, c; i < n; i++) {
        cin >> a >> b >> c;
        G[a].ep(b, c);
        G[b].ep(a, c);
    }
    ll ans = 0;
    for(int i = 1; i <= n; i++) {
        vis[i] = i;
        ll lans = dfs(i);
        debug("i = %d, lans = %lld\n", i, lans);
        ans = max(ans, lans);
    }
    cout << ans << endl;
}

Compilation message (stderr)

beads.cpp: In function 'll dfs(int)':
beads.cpp:19:20: warning: statement has no effect [-Wunused-value]
   19 | #define debug(...) 42
      |                    ^~
beads.cpp:52:9: note: in expansion of macro 'debug'
   52 |         debug("x = %d, u = %d, sum = %lld\n", x, u, sum);
      |         ^~~~~
beads.cpp:19:20: warning: statement has no effect [-Wunused-value]
   19 | #define debug(...) 42
      |                    ^~
beads.cpp:63:9: note: in expansion of macro 'debug'
   63 |         debug("got alternator (%lld, %lld) and (%lld, %lld)\n", w1, u1, w2, u2);
      |         ^~~~~
beads.cpp:19:20: warning: statement has no effect [-Wunused-value]
   19 | #define debug(...) 42
      |                    ^~
beads.cpp:66:5: note: in expansion of macro 'debug'
   66 |     debug("up[%d] = %lld, dp[%d] = %lld\n", x, up[x], x, dp[x]);
      |     ^~~~~
beads.cpp: In function 'int main()':
beads.cpp:19:20: warning: statement has no effect [-Wunused-value]
   19 | #define debug(...) 42
      |                    ^~
beads.cpp:86:9: note: in expansion of macro 'debug'
   86 |         debug("i = %d, lans = %lld\n", i, lans);
      |         ^~~~~

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