Submission #593091

#	Time	Username	Problem	Language	Result	Execution time	Memory
593091		Jomnoi	Rainforest Jumps (APIO21_jumps)	C++17	0 / 100	250 ms	51244 KiB

jumps

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

const int MAX_N = 2e5 + 5;
const int INF = 1e9 + 7;

int N;
int H[MAX_N];
int L[MAX_N], R[MAX_N], nxt[2][MAX_N][20];
int table[MAX_N][20];

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

        table[i][0] = H[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]) {
            stk.pop();
        }

        if(!stk.empty()) {
            L[i] = stk.top();
        }
        stk.push(i);
    }
    while(!stk.empty()) {
        stk.pop();
    }

    for(int i = N; i >= 1; i--) {
        while(!stk.empty() and H[stk.top()] < H[i]) {
            stk.pop();
        }

        if(!stk.empty()) {
            R[i] = stk.top();
        }
        stk.push(i);
    }

    for(int i = 1; i <= N; i++) {
        nxt[0][H[i]][0] = H[R[i]];
        nxt[1][H[i]][0] = max(H[L[i]], H[R[i]]);
        for(int j = 1; j < 20; j++) {
            nxt[0][H[i]][j] = nxt[0][nxt[0][H[i]][j - 1]][j - 1];
            nxt[1][H[i]][j] = nxt[1][nxt[1][H[i]][j - 1]][j - 1];
        }
    }
}

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

int minimum_jumps(int A, int B, int C, int D) {
    A++, B++, C++, D++;
    int maxLeft = get_max(A, B);
    int maxMid = get_max(B + 1, C - 1);
    int maxRight = get_max(C, D);

    if(max(maxLeft, maxMid) > maxRight) {
        return -1;
    }

    int ans = 0;
    int l = A, r = B, now;
    while(l <= r) {
        int mid = (l + r) / 2;

        int mx = get_max(mid, B);
        if(mx < maxRight) {
            now = mx;
            r = mid - 1;
        }
        else {
            l = mid + 1;
        }
    }

    for(int i = 19; i >= 0; i--) {
        if(nxt[1][now][i] != 0 and nxt[1][now][i] < maxRight) {
            now = nxt[1][now][i];
            ans += (1<<i);
        }
    }
    for(int i = 19; i >= 0; i--) {
        if(nxt[0][now][i] != 0 and nxt[0][now][i] < maxRight) {
            now = nxt[0][now][i];
            ans += (1<<i);
        }
    }
    return ans + 1;
}

Compilation message (stderr)

jumps.cpp: In function 'int minimum_jumps(int, int, int, int)':
jumps.cpp:97:25: warning: 'now' may be used uninitialized in this function [-Wmaybe-uninitialized]
   97 |         if(nxt[1][now][i] != 0 and nxt[1][now][i] < maxRight) {
      |            ~~~~~~~~~~~~~^

• 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