Submission #599871

#	Time	Username	Problem	Language	Result	Execution time	Memory
599871		jophyyjh	Lost in the cycle (IOI19_cycle)	C++14	100 / 100	1 ms	288 KiB

cycle

/**
 * Simple.
 * 
 * Steps needed: log_2(n)
 * Implementation 1
*/

#include <bits/stdc++.h>
#include "cycle.h"


int n;
int pos = 0;

// treat our initial (unknown) starting room as room 0. Provides jumping with
// absolute coordinate
inline int absolute_jump(int k) {
    int steps = (k - pos + n) % n;
    pos = k;
    bool ans = jump(steps);
    // std::cerr << k << ' ' << ans << std::endl;
    return ans;
}

void escape(int _n) {
    n = _n;
    bool a = absolute_jump(0), b = absolute_jump(n / 2);
    assert(a || b);
    if (a && b) {
        if (absolute_jump(1))
            absolute_jump(n / 2);
        else
            absolute_jump(0);
        return;
    }
    int left = 0, right = n / 2;
    if (b && !a) {
        std::swap(left, right);
        std::swap(a, b);
    }
    assert(a && !b);

    while (left != right) {
        int dist = (right - left + n) % n;
        int mid = left + (dist + 1) / 2;
        if (absolute_jump(mid))
            left = (mid + n) % n;
        else
            right = (mid - 1 + n) % n;
    }
    absolute_jump(left);
}

• Subtask 1: 11 / 11
• Subtask 2: 33 / 33
• Subtask 3: 56 / 56