Gerbil's run

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

using ld = long double;
using ll = long long;

const ld PI = M_PI;

const ll mult = 1000000;
const int range = 300000;

ld r = 0;
ld totalLen = 0;

ld eps = 1e-11;

bool check(ld alpha, ld extra)
{
    if (alpha < 0 || alpha + extra + eps >= 1)
        return false;
    ld x = totalLen / (1 + alpha);
    if ((ll)x % 2 == 1) {
        return false;
    }
    if (alpha + totalLen - x + eps >= 1) {
        return false;
    }
    return true;
}

pair<pair<ll, ll>, pair<ll, ll>> getAlpha()
{
    if (check(0, 0))
    {
        return {{0, 2}, {0, 2}};
    }

    vector<pair<ll, ll>> extras = {{0, 2}, {1, 4}, {1, 2}, {3, 4}};

    for (auto extra : extras) {
        totalLen -= (ld)extra.first / extra.second;

        ld x = floor(totalLen);
        ld b = totalLen - x;

        
        ld alphaStart = (totalLen) / (totalLen + b + 1) - 1;
        ll enumer = (ll)(alphaStart * mult);
        for (ll alphaEnum = enumer - range; alphaEnum < enumer + range; ++alphaEnum)
        {
            if (check((ld)alphaEnum / mult, (ld)extra.first / extra.second))
            {
                return {{alphaEnum, mult}, extra};
            }
        }

        enumer = 0;
        for (ll alphaEnum = enumer - range; alphaEnum < enumer + range; ++alphaEnum)
        {
            if (check((ld)alphaEnum / mult, (ld)extra.first / extra.second))
            {
                return {{alphaEnum, mult}, extra};
            }
        }

        totalLen += (ld)extra.first / extra.second;
    }
    

    assert(false);
    return {{0, 0}, {0, 0}};
}

int main()
{
    ios::sync_with_stdio(false);
    cin.tie(0);

    // for (int r1 = 1; r1 < 1001; ++r1) {
    //     cout << r1 << "\n";
    //     r = r1;
    //     totalLen = (2 * PI * r);

    //     auto alpha = getAlpha();
    // }

    cin >> r;
    totalLen = (2 * PI * r);

    auto [alpha, extra] = getAlpha();
    pair<ll, ll> len = {alpha.first + alpha.second, alpha.second};
    pair<ll, ll> prev = {0, len.second};
    pair<ll, ll> pos = {len.first, len.second};

    int i = 0;
    while ((ld)pos.first / pos.second < totalLen)
    {
        cout << prev.first << '/' << prev.second << ' ' << pos.first << '/' << pos.second << '\n';
        ++i;

        pos.first += len.first;
        prev = pos;
        if (i == 1) {
            pos.first += extra.first * (pos.second / extra.second); 
        } 
        pos.first += len.first;
        
    }

    return 0;
}

Test 1

Verdict: ACCEPTED

Test 2

Verdict: ACCEPTED

Test 3

Verdict: ACCEPTED

Test 4

Verdict: WRONG ANSWER

Test 5

Verdict: WRONG ANSWER

Test 6

Verdict: WRONG ANSWER

Test 7

Verdict: WRONG ANSWER

Test 8

Verdict: ACCEPTED

Test 9

Verdict: ACCEPTED

Test 10

Verdict: ACCEPTED

Test 11

Verdict: WRONG ANSWER

Test 12

Verdict: WRONG ANSWER

Test 13

Verdict: WRONG ANSWER

Test 14

Verdict: WRONG ANSWER

Test 15

Verdict: ACCEPTED

Test 16

Verdict: ACCEPTED

Test 17

Verdict: ACCEPTED

Test 18

Verdict: WRONG ANSWER

Test 19

Verdict: WRONG ANSWER

Test 20

Verdict: WRONG ANSWER

Test 21

Verdict: ACCEPTED

Test 22

Verdict: WRONG ANSWER

Test 23

Verdict: ACCEPTED

Test 24

Verdict: ACCEPTED

Test 25

Verdict: ACCEPTED

Test 26

Verdict: ACCEPTED

Test 27

Verdict: ACCEPTED

Test 28

Verdict: WRONG ANSWER

Test 29

Verdict: WRONG ANSWER

Test 30

Verdict: WRONG ANSWER

Test 31

Verdict: ACCEPTED

Test 32

Verdict: ACCEPTED

Test 33

Verdict: WRONG ANSWER

Test 34

Verdict: WRONG ANSWER

Test 35

Verdict: WRONG ANSWER

Test 36

Verdict: ACCEPTED

Test 37

Verdict: ACCEPTED

Test 38

Verdict: ACCEPTED

Test 39

Verdict: WRONG ANSWER

Test 40

Verdict: ACCEPTED

Test 41

Verdict: ACCEPTED

Test 42

Verdict: ACCEPTED

Test 43

Verdict: ACCEPTED

Test 44

Verdict: ACCEPTED

Test 45

Verdict: WRONG ANSWER