Submission #716714

#	Time	Username	Problem	Language	Result	Execution time	Memory
716714		aryan12	Rainforest Jumps (APIO21_jumps)	C++17	0 / 100	165 ms	26628 KiB

jumps

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

const int MAXN = 2e5 + 5;
int dp_min[19][MAXN], dp_max[19][MAXN];
vector<int> H;
int N;

void init(int n, std::vector<int> h) 
{
    stack<int> s;
    N = n;
    for(int i = 0; i < h.size(); i++)
    {
        H.push_back(h[i]);
    }
    for(int i = 0; i < N; i++)
    {
        while(!s.empty() && H[s.top()] < H[i])
        {
            s.pop();
        }
        if(s.empty())
        {
            dp_min[0][i] = -1;
        }
        else
        {
            dp_min[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())
        {
            dp_max[0][i] = -1;
        }
        else
        {
            dp_max[0][i] = s.top();
        }
        s.push(i);
        if((dp_max[0][i] < dp_min[0][i] && dp_max[0][i] != -1) || (dp_min[0][i] == -1))
        {
            swap(dp_min[0][i], dp_max[0][i]);
        }
    }
    for(int i = 1; i < 19; i++)
    {
        for(int j = 0; j < N; j++)
        {
            dp_min[i][j] = (dp_min[i - 1][j] == -1) ? -1 : dp_min[i - 1][dp_min[i - 1][j]];
            dp_max[i][j] = (dp_max[i - 1][j] == -1) ? -1 : dp_max[i - 1][dp_max[i - 1][j]];
            assert(dp_max[i][j] == -1 || H[dp_max[i][j]] >= H[dp_min[i][j]]);
        }
    }
}

int minimum_jumps(int A, int B, int C, int D) 
{
    // A = B && C = D
    int ans = 0;
    for(int i = 18; i >= 0; i--)
    {
        if(dp_max[i][A] != -1 && H[dp_max[i][A]] <= H[C])
        {
            ans += (1 << i);
            A = dp_max[i][A];
        }
    }
    for(int i = 18; i >= 0; i--)
    {
        if(dp_min[i][A] != -1 && H[dp_min[i][A]] <= H[C])
        {
            ans += (1 << i);
            A = dp_min[i][A];
        }
    }
    if(H[A] != H[C])
    {
        return -1;
    }
    return ans;
}

Compilation message (stderr)

jumps.cpp: In function 'void init(int, std::vector<int>)':
jumps.cpp:15:22: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   15 |     for(int i = 0; i < h.size(); i++)
      |                    ~~^~~~~~~~~~

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