Submission #438073

#	Time	Username	Problem	Language	Result	Execution time	Memory
438073		cheeheng	Rainforest Jumps (APIO21_jumps)	C++14	12 / 100	4069 ms	164200 KiB

jumps

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

typedef pair<int, int> ii;

int nextGreater[200005][20];
int prevGreater[200005][20];
int indx[200005];
int log2_[200005];
ii val[200005][20];
int best[200005][20];
int A1[200005];

int M;

void init2(){
    for(int i = 0; i < M; i ++){
        val[i][0] = ii(A1[i], i);
    }

    for(int k = 1; k < 20; k ++){
        for(int i = 0; i <= M-(1<<k); i ++){
            val[i][k] = max(val[i][k-1], val[i+(1<<(k-1))][k-1]);
        }
    }

    log2_[1] = 0;
    for(int i = 2; i <= M; i ++){
        log2_[i] = log2_[i>>1] + 1;
    }
}

ii findMax(int l, int r){
    int k = log2_[r-l+1];
    return max(val[l][k], val[r-(1<<k)+1][k]);
}

void init(int N, std::vector<int> H){
    M = N;

    for(int i = 0; i < N; i ++){
        A1[i] = H[i];
    }

    init2();

    for(int i = 0; i < N; i ++){
        nextGreater[i][0] = N;
        prevGreater[i][0] = -1;
    }

    vector<ii> stack1 = vector<ii>();
    for(int i = 0; i < N; i ++){
        while(!stack1.empty()){
            ii temp = stack1.back();

            if(temp.first < H[i]){
                nextGreater[temp.second][0] = i;
                stack1.pop_back();
            }else{
                break;
            }
        }
        stack1.emplace_back(H[i], i);
    }

    stack1 = vector<ii>();
    for(int i = N-1; i >= 0; i --){
        while(!stack1.empty()){
            ii temp = stack1.back();

            if(temp.first < H[i]){
                prevGreater[temp.second][0] = i;
                stack1.pop_back();
            }else{
                break;
            }
        }
        stack1.emplace_back(H[i], i);
    }

    /*for(int i = 0; i < N; i ++){
        printf("nextGreater[%d]=%d\n", i, nextGreater[i][0]);
    }

    for(int i = 0; i < N; i ++){
        printf("prevGreater[%d]=%d\n", i, prevGreater[i][0]);
    }*/

    for(int k = 1; k < 20; k ++){
        for(int i = 0; i < N; i ++){
            if(nextGreater[i][k-1] == N){
                nextGreater[i][k] = N;
            }else{
                nextGreater[i][k] = nextGreater[nextGreater[i][k-1]][k-1];
            }

            if(prevGreater[i][k-1] == -1){
                prevGreater[i][k] = -1;
            }else{
                prevGreater[i][k] = prevGreater[prevGreater[i][k-1]][k-1];
            }
        }
    }

    for(int i = 0; i < N; i ++){
        int X2 = i;
        int X3, X4;
        if(prevGreater[X2][0] == -1){
            X3 = nextGreater[X2][0];
            X4 = prevGreater[X2][0];
        }else if(nextGreater[X2][0] == M){
            X3 = prevGreater[X2][0];
            X4 = nextGreater[X2][0];
        }else if(A1[prevGreater[X2][0]] > A1[nextGreater[X2][0]]){
            X3 = prevGreater[X2][0];
            X4 = nextGreater[X2][0];
        }else{
            X3 = nextGreater[X2][0];
            X4 = prevGreater[X2][0];
        }
        best[i][0] = X3;
        if(best[i][0] == M){best[i][0] = -1;}
    }

    for(int k = 1; k < 20; k ++){
        for(int i = 0; i < N; i ++){
            if(best[i][k-1] == -1){
                best[i][k] = -1;
            }else{
                best[i][k] = best[best[i][k-1]][k-1];
            }
        }
    }
}

int minimum_jumps(int A, int B, int C, int D){
    assert(0 <= A && A <= B && B < C && C <= D && D <= M-1);

    ii maxValCD = findMax(C, D);
    int maxIndxCD = prevGreater[maxValCD.second][0];
    //printf("maxValCD=%d\n", maxValCD);
    A = max(maxIndxCD+1, A);

    if(A > B){return -1;}

    ii maxValAB = findMax(A, B);
    int X = maxValAB.second;

    int cutOffIndx = X;
    for(int k = 19; k >= 0; k --){
        if(nextGreater[cutOffIndx][k] != M && nextGreater[cutOffIndx][k] < C){
            cutOffIndx = nextGreater[cutOffIndx][k];
        }
    }
    cutOffIndx = nextGreater[cutOffIndx][0];
    assert(cutOffIndx >= C && cutOffIndx <= D);

    int ans = 0;

    int X5 = X;
    int totalDist = 0;
    for(int k = 19; k >= 0; k --){
        int temp = best[X5][k];
        if(temp != -1 && val[temp] < val[cutOffIndx]){
            totalDist += (1<<k);
            X5 = temp;
        }
    }

    int X2 = X;
    totalDist = max(0, totalDist-min(200, M));
    ans += totalDist;
    for(int k = 19; k >= 0; k --){
        int temp = best[X2][k];
        if(temp != -1 && totalDist >= (1<<k)){
            totalDist -= (1<<k);
            X2 = temp;
        }
    }
    assert(X2 != -1 && X2 < C && X2 >= A);

    while(X2 < C){
        int X3, X4;
        if(prevGreater[X2][0] == -1){
            X3 = nextGreater[X2][0];
            X4 = prevGreater[X2][0];
        }else if(nextGreater[X2][0] == M){
            X3 = prevGreater[X2][0];
            X4 = nextGreater[X2][0];
        }else if(A1[prevGreater[X2][0]] > A1[nextGreater[X2][0]]){
            X3 = prevGreater[X2][0];
            X4 = nextGreater[X2][0];
        }else{
            X3 = nextGreater[X2][0];
            X4 = prevGreater[X2][0];
        }

        //printf("X2=%d; X3=%d; X4=%d\n", X2, X3, X4);
        if(X4 >= C && X4 <= D){
            X2 = X4;
        }else if(A1[X3] > maxValCD.first){
            X2 = X4;
        }else{
            X2 = X3;
        }
        //printf("X2=%d\n", X2);
        ans ++;
        assert(X2 >= 0 && X2 < M);
    }

    return ans;
}

Compilation message (stderr)

jumps.cpp: In function 'void init(int, std::vector<int>)':
jumps.cpp:109:17: warning: variable 'X4' set but not used [-Wunused-but-set-variable]
  109 |         int X3, X4;
      |                 ^~

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