Submission #478161

#	Time	Username	Problem	Language	Result	Execution time	Memory
478161		Yazan_Alattar	Rainforest Jumps (APIO21_jumps)	C++14	100 / 100	1491 ms	50580 KiB

jumps

#include "jumps.h"
#include <iostream>
#include <fstream>
#include <vector>
#include <cstring>
#include <algorithm>
#include <set>
#include <map>
#include <queue>
#include <list>
#include <utility>
#include <cmath>
#include <numeric>
using namespace std;
typedef long long ll;
#define F first
#define S second
#define pb push_back
#define endl "\n"
#define all(x) x.begin(), x.end()
const int M = 200007;
const ll inf = 1e9;
const ll mod = 1e9 + 7;
const double pi = acos(-1);
const int dx[] = {1, 0, -1, 0}, dy[] = {0, 1, 0, -1};

int a[M], l[M][20], r[M][20], hi[M][20];

void init(int n, vector <int> H)
{
    for(int i = 1; i <= n; ++i) a[i] = H[i - 1];
    vector <int> v;
    a[0] = inf; a[n + 1] = inf;
    for(int i = 0; i <= n + 1; ++i){
        while(v.size() && a[v.back()] <= a[i]) v.pop_back();
        if(v.size()) l[i][0] = v.back();
        else l[i][0] = i;
        v.pb(i);
    }
    v.clear();
    for(int i = n + 1; i >= 0; --i){
        while(v.size() && a[v.back()] < a[i]) v.pop_back();
        if(v.size()) r[i][0] = v.back();
        else r[i][0] = i;
        v.pb(i);
    }
    for(int i = 0; i <= n + 1; ++i) hi[i][0] = (a[r[i][0]] > a[l[i][0]] ? r[i][0] : l[i][0]);
    for(int j = 1; j < 20; ++j){
        for(int i = 0; i <= n + 1; ++i){
            l[i][j] = l[l[i][j - 1]][j - 1];
            r[i][j] = r[r[i][j - 1]][j - 1];
            hi[i][j] = hi[hi[i][j - 1]][j - 1];
        }
    }
    return;
}

int get(int A, int B)
{
    for(int i = 19; i >= 0; --i)
        if(r[A][i] <= B)
            A = r[A][i];
    return A;
}

int minimum_jumps(int A, int B, int C, int D)
{
    ++A; ++B; ++C; ++D;
    if(B + 1 == C) return (r[B][0] <= D ? 1 : -1);
    int mid = get(B + 1, C - 1);
    if(a[B] > a[mid]) return (r[B][0] <= D ? 1 : -1);
    int p = B;
    for(int i = 19; i >= 0; --i)
        if(l[p][i] >= A && a[l[p][i]] < a[mid])
            p = l[p][i];
    int ret = 0;
    if(l[p][0] >= A){
        if(r[l[p][0]][0] <= D) return 1;
    }
    else{
        for(int i = 19; i >= 0; --i){
            if(a[hi[p][i]] <= a[mid]){
                ret += (1 << i);
                p = hi[p][i];
            }
        }
        if(p == mid) return (r[p][0] <= D ? ret + 1 : -1);
        if(l[p][0] && r[l[p][0]][0] <= D) return ret + 2;
    }
    for(int i = 19; i >= 0; --i){
        if(r[p][i] < C){
            ret += (1 << i);
            p = r[p][i];
        }
    }
    return (r[p][0] >= C && r[p][0] <= D ? ret + 1 : -1);
}

// Don't forget special cases. (n = 1?)
// Look for the constraints. (Runtime array? overflow?)

• 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