Submission #964611

#	Time	Username	Problem	Language	Result	Execution time	Memory
964611		kilkuwu	Rainforest Jumps (APIO21_jumps)	C++17	33 / 100	4082 ms	13500 KiB

jumps

#include "jumps.h"

#include <bits/stdc++.h>

template <typename Info, typename Merge = std::plus<Info>>
struct IterativeSegmentTree {
  int n;
  std::vector<Info> T;

  IterativeSegmentTree() {}

  IterativeSegmentTree(int _n) : n(2 << std::__lg(_n)), T(2 * n, Info()){};

  template <typename Type>
  IterativeSegmentTree(const std::vector<Type>& a) : n(2 << std::__lg(a.size())), T(2 * n, Info()) {
    for (int i = n; i < n + (int) a.size(); i++) {
      T[i] = a[i - n];
    }
    for (int i = n - 1; i > 0; i--) {
      T[i] = Merge()(T[i << 1], T[i << 1 | 1]);
    }
  }

  template <typename Iterator>
  IterativeSegmentTree(Iterator first, Iterator last) : n(2 << std::__lg(distance(first, last))), T(2 * n, Info()) {
    int id = n;
    for (Iterator it = first; it != last; it++) {
      T[id++] = *it;
    }
    for (int i = n - 1; i > 0; i--) {
      T[i] = Merge()(T[i << 1], T[i << 1 | 1]);
    }
  }

  void update(int p, const Info& v) {
    for (T[p += n] = v; p >>= 1;) {
      T[p] = Merge()(T[p << 1], T[p << 1 | 1]);
    }
  }

  Info query(int l, int r) {
    Info resl = Info(), resr = Info();
    for (l += n, r += n; l < r; l >>= 1, r >>= 1) {
      if (l & 1) resl = Merge()(resl, T[l++]);
      if (r & 1) resr = Merge()(T[--r], resr);
    }
    return Merge()(resl, resr);
  }
};

struct Info {
  std::pair<int, int> mn = {1e9, -1}, mx = {-1e9, -1};
};

Info operator+(const Info& a, const Info& b) {
  return {std::min(a.mn, b.mn), std::max(a.mx, b.mx)};
}

constexpr int mxN = 200002;
int L[mxN];
int R[mxN];
int N;

std::vector<int> H;

IterativeSegmentTree<Info> tree;

void init(int _N, std::vector<int> _H) {
  N = _N;
  H = _H;
  std::stack<int> st;
  for (int i = 0; i < N; i++) {
    while (st.size() && H[st.top()] <= H[i]) {
      st.pop();
    }
    L[i] = st.empty() ? -1 : st.top();
    st.push(i);
  }

  while (st.size()) st.pop();

  for (int i = N - 1; i >= 0; i--) {
    while (st.size() && H[st.top()] <= H[i]) {
      st.pop();
    }
    R[i] = st.empty() ? -1 : st.top();
    st.push(i);
  }

  tree = IterativeSegmentTree<Info>(N);
  for (int i = 0; i < N; i++) {
    tree.update(i, {{H[i], i}, {H[i], i}});
  }
}

// we answer them in O(n)
int minimum_jumps(int A, int B, int C, int D) {
  int sz_mid = C - B - 1;

  auto bl = tree.query(A, B + 1);
  auto br = tree.query(C, D + 1);
  if (sz_mid > 0) {
    auto bmid = tree.query(B + 1, C);

    if (bmid.mx.first >= br.mx.first) {
      return -1;
    }
  }

  if (H[B] >= br.mx.first) return -1;

  std::vector<int> dp(N, -1);
  std::queue<int> q;
  for (int i = A; i <= B; i++) {
    dp[i] = 0;
    q.push(i);
  }

  while (q.size()) {
    int u = q.front();
    q.pop();

    for (int v : {L[u], R[u]}) {
      if (v == -1) continue;
      if (dp[v] != -1) continue;
      dp[v] = dp[u] + 1;
      q.emplace(v);
    }
  }

  int ans = 1e9;
  for (int i = C; i <= D; i++) {
    if (dp[i] != -1) ans = std::min(ans, dp[i]);
  }
  return ans;
}

Compilation message (stderr)

jumps.cpp: In function 'int minimum_jumps(int, int, int, int)':
jumps.cpp:100:8: warning: variable 'bl' set but not used [-Wunused-but-set-variable]
  100 |   auto bl = tree.query(A, B + 1);
      |        ^~

• Subtask 1: 0 / 4
• Subtask 2: 8 / 8
• Subtask 3: 13 / 13
• Subtask 4: 12 / 12
• Subtask 5: 0 / 23
• Subtask 6: 0 / 21
• Subtask 7: 0 / 19