Submission #716718

#	Time	Username	Problem	Language	Result	Execution time	Memory
716718		aryan12	Rainforest Jumps (APIO21_jumps)	C++17	27 / 100	1447 ms	79728 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> seg[MAXN * 4]; // at position i stores the value H[i]
vector<int> H, REV;
int N;

void Build(int left, int right, int pos)
{
    if(left == right)
    {
        seg[pos].push_back(H[left]);
        return;
    }
    int mid = (left + right) / 2;
    Build(left, mid, pos * 2);
    Build(mid + 1, right, pos * 2 + 1);
    merge(seg[pos * 2].begin(), seg[pos * 2].end(), seg[pos * 2 + 1].begin(), seg[pos * 2 + 1].end(), back_inserter(seg[pos]));
}

int Query(int l, int r, int pos, int ql, int qr, int qval)
{
    // cout << "qpos = " << ql << ", " << qr << ", qval = " << qval << "\n";
    if(ql > r || l > qr)
    {
        return -1;
    }
    if(ql <= l && r <= qr)
    {
        int cur_pos = lower_bound(seg[pos].begin(), seg[pos].end(), qval) - seg[pos].begin() - 1;
        if(cur_pos == -1)
        {
            return -1;
        }
        return seg[pos][cur_pos];
    }
    int mid = (l + r) >> 1;
    return max(Query(l, mid, pos * 2, ql, qr, qval), Query(mid + 1, r, pos * 2 + 1, ql, qr, qval));
}

void init(int n, std::vector<int> h) 
{
    stack<int> s;
    N = n;
    REV.resize(N + 1);
    for(int i = 0; i < h.size(); i++)
    {
        H.push_back(h[i]);
        REV[H[i]] = i;
    }
    Build(0, N - 1, 1);
    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_min[0][i] == -1 || (dp_max[0][i] != -1 && H[dp_max[0][i]] < H[dp_min[0][i]]))
        {
            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
    // cout << "---- ---- ---- ---- ----\n";
    // cout << "A = " << A << ", B = " << B << "\n";
    int query_result = Query(0, N - 1, 1, A, B, H[C]);
    // cout << "query_result = " << query_result << "\n";
    if(query_result == -1)
    {
        return -1;
    }
    A = REV[query_result];
    B = A;
    // cout << "A = " << A << ", B = " << B << "\n";
    // cout << "---- ---- ---- ---- ----\n";
    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:50:22: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   50 |     for(int i = 0; i < h.size(); i++)
      |                    ~~^~~~~~~~~~

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