Submission #314919

#	Time	Username	Problem	Language	Result	Execution time	Memory
314919		VROOM_VARUN	Race (IOI11_race)	C++14	100 / 100	1701 ms	59924 KiB

race

/*
ID: varunra2
LANG: C++
TASK: race
*/

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

#ifdef DEBUG
#include "lib/debug.h"
#define debug(...) cerr << "[" << #__VA_ARGS__ << "]:", debug_out(__VA_ARGS__)
#define debug_arr(...) \
  cerr << "[" << #__VA_ARGS__ << "]:", debug_arr(__VA_ARGS__)
#pragma GCC diagnostic ignored "-Wsign-compare"
//#pragma GCC diagnostic ignored "-Wunused-parameter"
//#pragma GCC diagnostic ignored "-Wunused-variable"
#else
#define debug(...) 42
#endif

#define EPS 1e-9
#define IN(A, B, C) assert(B <= A && A <= C)
#define INF (int)1e9
#define MEM(a, b) memset(a, (b), sizeof(a))
#define MOD 1000000007
#define MP make_pair
#define PB push_back
#define all(cont) cont.begin(), cont.end()
#define rall(cont) cont.end(), cont.begin()
#define x first
#define y second

const double PI = acos(-1.0);
typedef long long ll;
typedef long double ld;
typedef pair<int, int> PII;
typedef map<int, int> MPII;
typedef multiset<int> MSETI;
typedef set<int> SETI;
typedef set<string> SETS;
typedef vector<int> VI;
typedef vector<PII> VII;
typedef vector<VI> VVI;
typedef vector<string> VS;

#define rep(i, a, b) for (int i = a; i < (b); ++i)
#define trav(a, x) for (auto& a : x)
#define sz(x) (int)(x).size()
typedef pair<int, int> pii;
typedef vector<int> vi;
#pragma GCC diagnostic ignored "-Wsign-compare"
// util functions

int n, k;

vector<VII> adj;
VVI centadj;
VI cent;
VI ret;

struct centroid {
  vector<bool> vis;
  VI sub;
  void init() {
    vis.assign(n, false);
    sub.resize(n);
    cent.resize(n);
    centadj.resize(n);
    adj.resize(n);
    ret.assign(n, 2 * INF);
  }

  int dfs(int u, int v) {
    sub[u] = 1;
    for (auto& x : adj[u]) {
      if (x.x != v and vis[x.x] == false) {
        sub[u] += dfs(x.x, u);
      }
    }
    return sub[u];
  }

  int getCent(int u, int siz, int v) {
    for (auto& x : adj[u]) {
      if (x.x != v and vis[x.x] == false) {
        if (sub[x.x] * 2 > siz) {
          return getCent(x.x, siz, u);
        }
      }
    }
    return u;
  }

  void centr(int u, int lev, int par = -1) {
    int c = getCent(u, dfs(u, -1), -1);
    cent[c] = ++lev;
    vis[c] = true;
    if (par != -1) {
      centadj[par].PB(c);
    }
    for (auto& x : adj[c]) {
      if (vis[x.x] == false) {
        centr(x.x, lev, c);
      }
    }
  }
} centroid1;

void dfs(int u, int v, int og, int dist1, int dist2, VII& cur) {
  if (cent[u] <= cent[og]) return;
  if (dist1 > 10 * k) return;  // you can do > k, but just to be safe lmao
  // also im doing this so i dont have to use long long
  cur.PB(MP(dist1, dist2));
  for (auto& x : adj[u]) {
    if (x.x == v) continue;
    dfs(x.x, u, og, dist1 + x.y, dist2 + 1, cur);
  }
}

void solve(int u) {
  // first you solve for all of your children
  trav(x, centadj[u]) { solve(x); }
  MPII mp;
  VII cur;
  mp[0] = 0;
  for (auto& x : adj[u]) {
    cur.clear();
    dfs(x.x, u, u, x.y, 1, cur);
    if (cur.empty()) continue;
    trav(y, cur) {
      if (mp[k - y.x] > 0) ret[u] = min(ret[u], mp[k - y.x] + y.y);
      if (y.x == k) {
        ret[u] = min(ret[u], y.y);
      }
    }

    trav(y, cur) {
      if (mp[y.x] == 0)
        mp[y.x] = y.y;
      else
        mp[y.x] = min(mp[y.x], y.y);
    }
  }
}

int best_path(int N, int K, int h[][2], int l[]) {
  n = N;
  k = K;
  centroid1.init();
  for (int i = 0; i < n - 1; i++) {
    int u, v, w;
    u = h[i][0], v = h[i][1], w = l[i];
    adj[u].PB(MP(v, w));
    adj[v].PB(MP(u, w));
  }
  centroid1.centr(0, 0);

  int root = min_element(all(cent)) - cent.begin();

  solve(root);

  int pr = *min_element(all(ret));
  if (pr == 2 * INF) return -1;
  return pr;
}

// int main() {
// #ifndef ONLINE_JUDGE
//   freopen("race.in", "r", stdin);
//   freopen("race.out", "w", stdout);
// #endif
//   cin.sync_with_stdio(0);
//   cin.tie(0);

//   int N, K;

//   cin >> N >> K;

//   int h[N - 1][2];
//   int l[N - 1];

//   for (int i = 0; i < N - 1; i++) {
//     cin >> h[i][0] >> h[i][1] >> l[i];
//   }

//   cout << best_path(N, K, h, l) << '\n';

//   return 0;
// }

• Subtask 1: 9 / 9
• Subtask 2: 12 / 12
• Subtask 3: 22 / 22
• Subtask 4: 57 / 57