Submission #876694

#	Time	Username	Problem	Language	Result	Execution time	Memory
876694		mgl_diamond	Dynamic Diameter (CEOI19_diameter)	C++17	49 / 100	5041 ms	20252 KiB

diameter

#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using ii = pair<ll, ll>;
 
#define foru(i, l, r) for(int i=(l); i<=(r); ++i)
#define ford(i, l, r) for(int i=(l); i>=(r); --i)
#define fore(x, v) for(auto &x : v)
#define all(x) (x).begin(), (x).end()
#define sz(x) (int)(x).size()
#define fi first
#define se second
#define file "input"

template<class T> bool minimize(T &a, T b) { if (a > b) { a = b; return 1; } return 0; }
template<class T> bool maximize(T &a, T b) { if (a < b) { a = b; return 1; } return 0; }

void setIO() {
  ios::sync_with_stdio(0);
  cin.tie(0); cout.tie(0);
  if (fopen(file".inp", "r")) {
    freopen(file".inp", "r", stdin);
    freopen(file".out", "w", stdout);
  }
}

const int MOD = 998244353;
const int N = 1e5+5;

struct edge {
  int u, v;
  ll w;
  int oth(int x) { return u^v^x; }
};
vector<edge> e;

bool allstar = 1, bintree = 1;

int n, q, up[N], par[N];
ll W;
vector<int> adj[N];
ll f[N];
ii nax[N];
set<ii> al;

void dfs_first(int u, int p, int h) {
  if (h > 20) bintree = 0;
  nax[u] = {0, 0};
  fore(i, adj[u]) {
    int v = e[i].oth(u);
    if (v == p) continue;
    up[i] = u;
    par[v] = u;
    dfs_first(v, u, h+1);
    maximize(f[u], f[v] + e[i].w);
    ll tmp = f[v] + e[i].w;
    if (tmp > nax[u].fi) swap(nax[u].fi, nax[u].se), nax[u].fi = tmp;
    else if (tmp > nax[u].se) nax[u].se = tmp;
  }
  al.insert({-nax[u].fi-nax[u].se, u});
}

void recalc(int u) {
  al.erase({-nax[u].fi-nax[u].se, u});
  nax[u] = {0, 0};
  f[u] = 0;
  fore(i, adj[u]) {
    int v = e[i].oth(u);
    if (v == par[u]) continue;
    maximize(f[u], f[v] + e[i].w);
    ll tmp = f[v] + e[i].w;
    if (tmp > nax[u].fi) swap(nax[u].fi, nax[u].se), nax[u].fi = tmp;
    else if (tmp > nax[u].se) nax[u].se = tmp;
  }
  al.insert({-nax[u].fi-nax[u].se, u});
}

int main() {
  setIO();

  cin >> n >> q >> W;
  e = vector<edge>(n-1);
  foru(i, 0, n-2) {
    int u, v;
    ll w;
    cin >> u >> v >> w;
    e[i] = {u, v, w};
    adj[u].push_back(i);
    adj[v].push_back(i);
  }

  allstar = (sz(adj[1]) == n-1);
  foru(i, 1, n) bintree &= (sz(adj[i]) > 2);

  if (allstar) foru(i, 0, n-2) al.insert({-e[i].w, i});
  else dfs_first(1, 0, 0);

  ll lst = 0;
  foru(i, 1, q) {
    ll ds, es;
    cin >> ds >> es;
    ds = (ds + lst) % (n - 1);
    es = (es + lst) % W;

    if (allstar) {
      al.erase({-e[ds].w, ds});
      e[ds].w = es;
      al.insert({-e[ds].w, ds});
      if (sz(al) == 1) lst = -(al.begin()->first);
      else lst = -(al.begin()->first + next(al.begin())->first);
    }
    else {
      int u = up[ds];
      e[ds].w = es;
      while (true) {
        recalc(u);
        if (u == 1) break;
        u = par[u];
      }
      lst = -(al.begin()->first);
    }
  
    cout << lst << "\n";
  }
}

Compilation message (stderr)

diameter.cpp: In function 'void setIO()':
diameter.cpp:22:12: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   22 |     freopen(file".inp", "r", stdin);
      |     ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~
diameter.cpp:23:12: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   23 |     freopen(file".out", "w", stdout);
      |     ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 11 / 11
• Subtask 2: 13 / 13
• Subtask 3: 7 / 7
• Subtask 4: 18 / 18
• Subtask 5: 0 / 24
• Subtask 6: 0 / 27