Submission #684064

#	Time	Username	Problem	Language	Result	Execution time	Memory
684064		MilosMilutinovic	Mountain Trek Route (IZhO12_route)	C++14	100 / 100	296 ms	29572 KiB

route

#include <bits/stdc++.h>

using namespace std;

int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  int n, k;
  cin >> n >> k;
  vector<int> a(n);
  for (int i = 0; i < n; i++) {
    cin >> a[i];
  }
  if (*min_element(a.begin(), a.end()) == *max_element(a.begin(), a.end())) {
    cout << 0 << '\n';
    return 0;
  }
  vector<int> par(n);
  vector<int> L(n);
  vector<int> R(n);
  vector<int> sz(n);
  for (int i = 0; i < n; i++) {
    par[i] = i;
    L[i] = i;
    R[i] = i;
    sz[i] = 1;
  }
  function<int(int)> Get = [&](int x) {
    return par[x] == x ? x : par[x] = Get(par[x]);
  };
  auto Unite = [&](int x, int y) {
    x = Get(x);
    y = Get(y);
    if (Get((R[y] + 1) % n) == x) {
      swap(x, y);
    }
    sz[x] += sz[y];
    par[y] = x;
    R[x] = R[y];
  };
  for (int i = 0; i < n; i++) {
    if (a[(i + 1) % n] == a[i]) {
      Unite(i, (i + 1) % n);
    }
  }
  auto Valid = [&](int i) {
    i = Get(i);
    int lx = Get((L[i] - 1 + n) % n);
    int rx = Get((R[i] + 1) % n);
    return a[i] < min(a[lx], a[rx]);
  };
  set<pair<int, int>> st;
  for (int i = 0; i < n; i++) {
    if (i == Get(i) && Valid(i)) {
      st.emplace(sz[i], i);
    }
  }
  auto Fix = [&](int x) {
    int lx = Get((L[x] - 1 + n) % n);
    int rx = Get((R[x] + 1) % n);
    int mn = min(a[lx], a[rx]);
    a[x] = mn;
    if (a[lx] == mn) {
      Unite(lx, x);
    }
    if (a[rx] == mn) {
      Unite(rx, x);
    }
    lx = Get(lx);
    rx = Get(rx);
    x = Get(x);
    if (Valid(lx)) {
      st.emplace(sz[lx], lx);
    }
    if (Valid(rx)) {
      st.emplace(sz[rx], rx);
    }
    if (Valid(x)) {
      st.emplace(sz[x], x);
    }
  };
  auto MaxOps = [&](int x) {
    int lx = Get((L[x] - 1 + n) % n);
    int rx = Get((R[x] + 1) % n);
    return min(a[lx], a[rx]) - a[x];
  };
  int ans = 0;
  while (!st.empty()) {
    auto it = st.begin();
    int i = Get(it->second);
    st.erase(it);
    int x = min(k / sz[i], MaxOps(i));
    k -= x * sz[i];
    ans += 2 * x;
    Fix(i);
  }
  cout << ans << '\n';
  return 0;
}

• Subtask 1: 100 / 100