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 = 400000;
const int range = 100;

ld r = 0;
ld totalLen = 0;

bool check(ld alpha) {
    if (alpha < 0 || alpha >= 1)
        return false;
    ld x = (2 * PI * r) / (1 + alpha);
    return (ll)x % 2 == 0;
}

pair<ll, ll> getAlpha() {
    if (check(0)) {
        return {0, 1};
    }
    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)) {
            return {alphaEnum, mult};
        }
    }

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

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

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

    auto alpha = 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};
    while((ld)pos.first / pos.second < totalLen) {
        cout << prev.first << '/' << prev.second << ' ' << pos.first << '/' << pos.second << '\n';
        pos.first += len.first;
        prev = pos;
        pos.first += len.first;
    }

    return 0;
}

Test 1

Verdict: ACCEPTED

Test 2

Verdict: ACCEPTED

Test 3

Verdict: ACCEPTED

Test 4

Verdict: RUNTIME ERROR

code: input/code.cpp:37: std::pair<long long int, long long int> getAlpha(): Assertion `false' failed.

Test 5

Verdict: RUNTIME ERROR

code: input/code.cpp:37: std::pair<long long int, long long int> getAlpha(): Assertion `false' failed.

Test 6

Verdict: RUNTIME ERROR

code: input/code.cpp:37: std::pair<long long int, long long int> getAlpha(): Assertion `false' failed.

Test 7

Verdict: RUNTIME ERROR

code: input/code.cpp:37: std::pair<long long int, long long int> getAlpha(): Assertion `false' failed.

Test 8

Verdict: ACCEPTED

Test 9

Verdict: ACCEPTED

Test 10

Verdict: ACCEPTED

Test 11

Verdict: RUNTIME ERROR

code: input/code.cpp:37: std::pair<long long int, long long int> getAlpha(): Assertion `false' failed.

Test 12

Verdict: RUNTIME ERROR

code: input/code.cpp:37: std::pair<long long int, long long int> getAlpha(): Assertion `false' failed.

Test 13

Verdict: RUNTIME ERROR

code: input/code.cpp:37: std::pair<long long int, long long int> getAlpha(): Assertion `false' failed.

Test 14

Verdict: RUNTIME ERROR

code: input/code.cpp:37: std::pair<long long int, long long int> getAlpha(): Assertion `false' failed.

Test 15

Verdict: ACCEPTED

Test 16

Verdict: ACCEPTED

Test 17

Verdict: ACCEPTED

Test 18

Verdict: RUNTIME ERROR

code: input/code.cpp:37: std::pair<long long int, long long int> getAlpha(): Assertion `false' failed.

Test 19

Verdict: RUNTIME ERROR

code: input/code.cpp:37: std::pair<long long int, long long int> getAlpha(): Assertion `false' failed.

Test 20

Verdict: RUNTIME ERROR

code: input/code.cpp:37: std::pair<long long int, long long int> getAlpha(): Assertion `false' failed.

Test 21

Verdict: ACCEPTED

Test 22

Verdict: RUNTIME ERROR

code: input/code.cpp:37: std::pair<long long int, long long int> getAlpha(): Assertion `false' failed.

Test 23

Verdict: ACCEPTED

Test 24

Verdict: ACCEPTED

Test 25

Verdict: ACCEPTED

Test 26

Verdict: ACCEPTED

Test 27

Verdict: ACCEPTED

Test 28

Verdict: RUNTIME ERROR

code: input/code.cpp:37: std::pair<long long int, long long int> getAlpha(): Assertion `false' failed.

Test 29

Verdict: RUNTIME ERROR

code: input/code.cpp:37: std::pair<long long int, long long int> getAlpha(): Assertion `false' failed.

Test 30

Verdict: RUNTIME ERROR

code: input/code.cpp:37: std::pair<long long int, long long int> getAlpha(): Assertion `false' failed.

Test 31

Verdict: ACCEPTED

Test 32

Verdict: ACCEPTED

Test 33

Verdict: RUNTIME ERROR

code: input/code.cpp:37: std::pair<long long int, long long int> getAlpha(): Assertion `false' failed.

Test 34

Verdict: RUNTIME ERROR

code: input/code.cpp:37: std::pair<long long int, long long int> getAlpha(): Assertion `false' failed.

Test 35

Verdict: RUNTIME ERROR

code: input/code.cpp:37: std::pair<long long int, long long int> getAlpha(): Assertion `false' failed.

Test 36

Verdict: ACCEPTED

Test 37

Verdict: ACCEPTED

Test 38

Verdict: ACCEPTED

Test 39

Verdict: RUNTIME ERROR

code: input/code.cpp:37: std::pair<long long int, long long int> getAlpha(): Assertion `false' failed.

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