Submission #620020

#	Time	Username	Problem	Language	Result	Execution time	Memory
620020		Jomnoi	Rainforest Jumps (APIO21_jumps)	C++17	100 / 100	1235 ms	77132 KiB

jumps

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

const int MAX_N = 2e5 + 5;

int N;
int H[MAX_N];
int pre[MAX_N][20], nxt1[MAX_N][20], nxt2[MAX_N][20];
vector <int> jump[MAX_N];
int table[MAX_N][20];

void init(int n, vector <int> h) {
    N = n;
    H[0] = H[N + 1] = N + 1;
    for(int i = 1; i <= N; i++) {
        H[i] = h[i - 1];

        table[i][0] = H[i];
        pre[i][0] = i;
    }

    for(int j = 1; j < 20; j++) {
        for(int i = 1; i + (1<<j) - 1 <= N; i++) {
            table[i][j] = max(table[i][j - 1], table[i + (1<<(j - 1))][j - 1]);
        }
    }

    stack <int> stk;
    for(int i = 1; i <= N; i++) {
        while(!stk.empty() and H[stk.top()] < H[i]) {
            jump[stk.top()].push_back(i);
            stk.pop();
        }
        if(!stk.empty()) {
            jump[i].push_back(stk.top());
            pre[i][0] = stk.top();
        }
        stk.push(i);
    }
    for(int i = 1; i <= N; i++) {
        while(jump[i].size() < 2) {
            jump[i].push_back(0);
        }

        sort(jump[i].begin(), jump[i].end(), [&](const int &a, const int &b) {
            return H[a] < H[b];
        });

        nxt1[i][0] = jump[i][0];
        nxt2[i][0] = jump[i][1];
    }
    
    for(int j = 1; j < 20; j++) {
        for(int i = 1; i <= N; i++) {
            pre[i][j] = pre[pre[i][j - 1]][j - 1];
            nxt1[i][j] = nxt1[nxt1[i][j - 1]][j - 1];
            nxt2[i][j] = nxt2[nxt2[i][j - 1]][j - 1];
        }
    }
}

int getMax(int l, int r) {
    int j = log2(r - l + 1);
    return max(table[l][j], table[r - (1<<j) + 1][j]);
}

int getIdx(int l, int r, int mx) {
    for(int i = 19; i >= 0; i--) {
        if(l <= pre[r][i] and H[pre[r][i]] < mx) {
            r = pre[r][i];
        }
    }
    return r;
}

int minimum_jumps(int A, int B, int C, int D) {
    A++, B++, C++, D++;

    int maxR = getMax(C, D);
    int st = getIdx(A, B, maxR);
    if(H[st] > maxR) {
        return -1;
    }
    if(B + 1 == C) {
        return 1;
    }

    int maxM = getMax(B + 1, C - 1);
    if(maxM > maxR) {
        return -1;
    }
    if(H[st] > maxM) {
        return 1;
    }

    int ans = 0;
    for(int i = 19; i >= 0; i--) {
        if(H[nxt2[st][i]] < maxM) {
            st = nxt2[st][i];
            ans += (1<<i);
        }
    }
    if(H[nxt2[st][0]] < maxR) {
        return ans + 2;
    }
    for(int i = 19; i >= 0; i--) {
        if(H[nxt1[st][i]] < maxM) {
            st = nxt1[st][i];
            ans += (1<<i);
        }
    }
    return ans + 2;
}

• 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