Submission #643982

#	Time	Username	Problem	Language	Result	Execution time	Memory
643982		colossal_pepe	Rainforest Jumps (APIO21_jumps)	C++17	100 / 100	1246 ms	47500 KiB

jumps

#include "jumps.h"

#include <iostream>
#include <vector>
#include <stack>
#include <algorithm>
using namespace std;
 
const int INF = 1e9;
 
int n, k;
vector<int> h, idx;
vector<vector<int>> st_max, st_u, st_r;

int rangeMax(int l, int r);

int getStart(int a, int b, int t);

int getMaxEndHeight(int c, int d);

int goRight(int s, int c);
 
void init(int N, vector<int> H) {
  n = N;
  h = H;
  k = __lg(n) + 1;
  idx.resize(n);
  st_max.resize(k, vector<int>(n));
  for (int i = 0; i < n; i++) {
    h[i]--;
    idx[h[i]] = i;
    st_max[0][i] = h[i];
  }
  st_u.resize(k, vector<int>(n));
  stack<int> s;
  for (int i = 0; i < n; i++) {
    while (not s.empty() and s.top() <= h[i]) s.pop();
    st_u[0][i] = s.empty() ? h[i] : s.top();
    s.push(h[i]);
  }
  while (not s.empty()) s.pop();
  st_r.resize(k, vector<int>(n));
  for (int i = n - 1; i >= 0; i--) {
    while (not s.empty() and s.top() <= h[i]) s.pop();
    st_u[0][i] = max(st_u[0][i], s.empty() ? h[i] : s.top());
    st_r[0][i] = s.empty() ? h[i] : s.top();
    s.push(h[i]);
  }
  for (int i = 1; i < k; i++) {
    for (int j = 0; j < n; j++) {
      if (j + (1 << i) - 1 < n) {
        st_max[i][j] = max(st_max[i - 1][j], st_max[i - 1][j + (1 << (i - 1))]);
      }
      st_u[i][j] = st_u[i - 1][idx[st_u[i - 1][j]]];
      st_r[i][j] = st_r[i - 1][idx[st_r[i - 1][j]]];
    }
  }
}
 
int minimum_jumps(int a, int b, int c, int d) {
  int e = idx[rangeMax(c, d)];
  int s = getStart(a, b, h[e]);
  if (s == -1) return -1;
  int hm = rangeMax(b + 1, c - 1);
  if (hm > h[e]) return -1;
  if (h[s] > hm) return 1;
  int jumps = 0;
  for (int bit = k - 1; bit >= 0; bit--) {
    if (st_u[bit][s] < hm) {
      jumps += (1 << bit);
      s = idx[st_u[bit][s]];
    }
  }
  if (st_u[0][s] < h[e]) return jumps + 2;
  for (int bit = k - 1; bit >= 0; bit--) {
    if (st_r[bit][s] < hm) {
      jumps += (1 << bit);
      s = idx[st_r[bit][s]];
    }
  }
  return jumps + 2;
}

int rangeMax(int l, int r) {
  if (l > r) return -1;
  int m = __lg(r - l + 1);
  return max(st_max[m][l], st_max[m][r - (1 << m) + 1]);
}

int getStart(int a, int b, int t) {
  int l = a, r = b;
  while (r - l) {
    int m = (l + r) / 2;
    if (rangeMax(m, b) > t) l = m + 1;
    else r = m;
  }
  if (rangeMax(l, b) > t) return -1;
  return idx[rangeMax(l, b)];
}

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