Submission #724182

#	Time	Username	Problem	Language	Result	Execution time	Memory
724182		fadi57	Rainforest Jumps (APIO21_jumps)	C++14	100 / 100	1248 ms	50480 KiB

jumps

#include "jumps.h"
#include <bits/stdc++.h>
#include <vector>
using namespace std;
 
const int MAXN = 2e5 + 5;
int left_jump[20][MAXN], right_jump[20][MAXN], higher[20][MAXN];
vector<int> H;
int N;
 
 
void init(int n, std::vector<int> h) 
{
    stack<int> s;
    N = n;
    H.push_back(1e9);
    for(int i = 0; i < h.size(); i++)
    {
        H.push_back(h[i]);
    }
    H.push_back(1e9);
    N += 2;
    for(int i = 0; i < N; i++)
    {
        while(!s.empty() && H[s.top()] < H[i])
        {
            s.pop();
        }
        if(s.empty())
        {
            left_jump[0][i] = i;
        }
        else
        {
            left_jump[0][i] = s.top();
        }
        s.push(i);
    }
    while(!s.empty())
    {
        s.pop();
    }
    for(int i = N - 1; i >= 0; i--)
    {
        while(!s.empty() && H[s.top()] < H[i])
        {
            s.pop();
        }
        if(s.empty())
        {
            right_jump[0][i] = i;
        }
        else
        {
            right_jump[0][i] = s.top();
        }
        s.push(i);
        higher[0][i] = (H[right_jump[0][i]] >= H[left_jump[0][i]]) ? right_jump[0][i] : left_jump[0][i];
    }
    for(int i = 1; i < 20; i++)
    {
        for(int j = 0; j < N; j++)
        {
            left_jump[i][j] = left_jump[i - 1][left_jump[i - 1][j]];
            right_jump[i][j] = right_jump[i - 1][right_jump[i - 1][j]];
            higher[i][j] = higher[i - 1][higher[i - 1][j]];
        }
    }
}
 
int max_height(int l, int r)
{
    int cur = l;
    for(int i = 19; i >= 0; i--)
    {
        if(right_jump[i][cur] <= r)
        {
            cur = right_jump[i][cur];
        }
    }
    return cur;
}
 
int minimum_jumps(int A, int B, int C, int D) 
{
    A++, B++, C++, D++;
    if(B == C - 1)
    {
        // no middle stuff
        return (right_jump[0][B] <= D) ? 1 : -1;
    }
    int middle_tallest_index = max_height(B + 1, C - 1);
    if(H[B] > H[middle_tallest_index])
    {
        return (right_jump[0][B] <= D) ? 1 : -1;
    }
    int current = B;
    for(int i = 19; i >= 0; i--)
    {
        if(A <= left_jump[i][current] && H[left_jump[i][current]] <= H[middle_tallest_index])
        {
            current = left_jump[i][current];
        }
    }
    int ans = 0;
    if(A <= left_jump[0][current])
    {
        if(right_jump[0][left_jump[0][current]] <= D)
        {
            return 1;
        }
    }
    else
    {
        for(int i = 19; i >= 0; i--)
        {
            if(H[higher[i][current]] <= H[middle_tallest_index])
            {
                ans += (1 << i);
                current = higher[i][current];
            }
        }
        if(current == middle_tallest_index)
        {
            return (right_jump[0][current] <= D) ? ans + 1 : -1;
        }
        if(left_jump[0][current] > 0 && right_jump[0][left_jump[0][current]] <= D)
        {
            return ans + 2;
        }
    }
    for(int i = 19; i >= 0; i--)
    {
        if(right_jump[i][current] < C)
        {
            ans += (1 << i);
            current = right_jump[i][current];
        }
    }
    ans++;
    current = right_jump[0][current];
    return (C <= current && current <= D) ? ans : -1;
}

Compilation message (stderr)

jumps.cpp: In function 'void init(int, std::vector<int>)':
jumps.cpp:17:22: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   17 |     for(int i = 0; i < h.size(); i++)
      |                    ~~^~~~~~~~~~

• 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