Thieves and Prisons

input/code.cpp: In function 'int main()':
input/code.cpp:113:34: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
    if (unfinishedReleases.size() > k)
        ~~~~~~~~~~~~~~~~~~~~~~~~~~^~~

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

#define rep(i, a, b) for(int i = a; i < (b); ++i)
#define trav(a, x) for(auto& a : x)
#define all(x) x.begin(), x.end()
#define allP(x) x->begin(), x->end()
#define sz(x) (int)(x).size()

// #define int ll

typedef long long ll;

const int inf = 0x3f3f3f3f;
const long long mod = 1000000007;

int main()
{
	cin.sync_with_stdio(false);
	cin.tie(NULL);
	// cin.exceptions(cin.failbit);
	// cout << setprecision(10);
	// cout << fixed;

	int n, k, m; cin >> n >> k >> m;

	vector<pair<char, int>> actions(m);
	for (int i = 0; i < m; i++)
	{
		char character; cin >> character;
		int prisoner; cin >> prisoner;
		prisoner--;

		actions[i] = make_pair(character, prisoner);
	}

	// Normal
	bool isPossible = true;
	vector<int> answers; answers.reserve(m);

	// Specifics
	unordered_set<int> tempImprisoned;

	while (actions.size() > 0 && actions.back().first == 'C')
	{
		if (tempImprisoned.find(actions.back().second) != tempImprisoned.end())
		{
			isPossible = false;
			actions.clear();
			break;
		}

		tempImprisoned.insert(actions.back().second);
		answers.push_back(0);

		actions.pop_back();
	}

	reverse(all(actions));

	// Specifics
	int latestReleaser = -1;

	int prisonReleaseIndex = 0;
	int lastPrisonCapturedIndex = -1;

	deque<pair<int, int>> unfinishedReleases;

	for (auto& action : actions)
	{
		char& c = action.first;
		int& prisoner = action.second;

		if (c == 'C')
		{
			if (latestReleaser == prisoner)
			{
				isPossible = false;
				break;
			}
			if (unfinishedReleases.size() > 0)
			{
				if (unfinishedReleases.front().second == prisoner)
				{
					lastPrisonCapturedIndex = unfinishedReleases[1].first;

					unfinishedReleases[1] = unfinishedReleases.front();
					unfinishedReleases.pop_front();
				}
				else
				{
					lastPrisonCapturedIndex = unfinishedReleases.front().first;

					unfinishedReleases.pop_front();
				}

				answers.push_back(lastPrisonCapturedIndex);
			}
			else
			{
				answers.push_back(lastPrisonCapturedIndex);
			}
		}
		else
		{
			latestReleaser = prisoner;
			unfinishedReleases.push_back(make_pair(prisonReleaseIndex, prisoner));

			answers.push_back(prisonReleaseIndex);
			prisonReleaseIndex++;
			prisonReleaseIndex %= k;

			if (unfinishedReleases.size() > k)
			{
				isPossible = false;
				break;
			}
		}
	}

	if (unfinishedReleases.size() > 0)
	{
		isPossible = false;
	}

	reverse(all(answers));

	if (isPossible == false)
	{
		cout << "IMPOSSIBLE";
	}
	else
	{
		for (auto& answer : answers)
		{
			cout << answer + 1 << ' ';
		}
	}

	return 0;
}

Test 1

Group: 2, 4, 5

Verdict: ACCEPTED

Test 2

Group: 2, 4, 5

Verdict: ACCEPTED

Test 3

Group: 2, 4, 5

Verdict: ACCEPTED

Test 4

Group: 2, 4, 5

Verdict: ACCEPTED

Test 5

Group: 2, 4, 5

Verdict: ACCEPTED

Test 6

Group: 4, 5

Verdict: ACCEPTED

Test 7

Group: 4, 5

Verdict: ACCEPTED

Test 8

Group: 4, 5

Verdict: ACCEPTED

Test 9

Group: 1, 3, 4, 5

Verdict: ACCEPTED

Test 10

Group: 1, 3, 4, 5

Verdict: ACCEPTED

Test 11

Group: 1, 3, 4, 5

Verdict: ACCEPTED

Test 12

Group: 1, 3, 4, 5

Verdict: ACCEPTED

Test 13

Group: 1, 3, 4, 5

Verdict: ACCEPTED

Test 14

Group: 1, 3, 4, 5

Verdict: ACCEPTED

Test 15

Group: 1, 3, 4, 5

Verdict: ACCEPTED

Test 16

Group: 1, 3, 4, 5

Verdict: ACCEPTED

Test 17

Group: 1, 2, 3, 4, 5

Verdict: ACCEPTED

Test 18

Group: 1, 3, 4, 5

Verdict: ACCEPTED

Test 19

Group: 2, 5

Verdict: ACCEPTED

Test 20

Group: 2, 5

Verdict: ACCEPTED

Test 21

Group: 2, 5

Verdict: ACCEPTED

Test 22

Group: 5

Verdict: ACCEPTED

Test 23

Group: 5

Verdict: ACCEPTED

Test 24

Group: 3, 4, 5

Verdict: ACCEPTED

Test 25

Group: 3, 4, 5

Verdict: ACCEPTED

Test 26

Group: 3, 4, 5

Verdict: ACCEPTED

Test 27

Group: 3, 4, 5

Verdict: ACCEPTED

Test 28

Group: 4, 5

Verdict: ACCEPTED

Test 29

Group: 4, 5

Verdict: ACCEPTED

Test 30

Group: 4, 5

Verdict: ACCEPTED

Test 31

Group: 4, 5

Verdict: ACCEPTED

Test 32

Group: 2, 4, 5

Verdict: ACCEPTED

Test 33

Group: 2, 4, 5

Verdict: ACCEPTED

Test 34

Group: 2, 4, 5

Verdict: ACCEPTED

Test 35

Group: 2, 4, 5

Verdict: ACCEPTED

Test 36

Group: 3, 5

Verdict: ACCEPTED

Test 37

Group: 3, 5

Verdict: ACCEPTED

Test 38

Group: 3, 5

Verdict: ACCEPTED

Test 39

Group: 3, 5

Verdict: ACCEPTED

Test 40

Group: 5

Verdict: ACCEPTED

Test 41

Group: 5

Verdict: ACCEPTED

Test 42

Group: 5

Verdict: ACCEPTED

Test 43

Group: 5

Verdict: ACCEPTED

Test 44

Group: 2, 5

Verdict: ACCEPTED

Test 45

Group: 2, 5

Verdict: ACCEPTED

Test 46

Group: 2, 5

Verdict: ACCEPTED

Test 47

Group: 2, 5

Verdict: ACCEPTED