Vaihdot

input/code.cpp: In function 'void solve(std::vector<int>&)':
input/code.cpp:9:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for (int i = 0; i < v.size(); ++i) {
                  ~~^~~~~~~~~~
input/code.cpp:11:9: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   if (i == v.size() - 1) {
       ~~^~~~~~~~~~~~~~~
input/code.cpp:18:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
    for (k = 0; k < v.size(); ++k) {
                ~~^~~~~~~~~~
input/code.cpp:37:26: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
    for (int j = i + 1; j < v.size(); ++j) {
                        ~~^~~~~~~~~~

#include <iostream>
#include <utility>
#include <vector>

using namespace std;

void solve(vector<int> &v) {
	vector<pair<int, int>> m;
	for (int i = 0; i < v.size(); ++i) {
		if (v[i] == i + 1) continue;
		if (i == v.size() - 1) {
			cout << -1 << endl;
			return;
		}
		if (v[i+1] == i + 1 && v[i] == i + 2) {
			int k;
			bool ok = false;
			for (k = 0; k < v.size(); ++k) {
				if (k == i || k == i + 1) continue;
				if (abs(v[k] - v[i+1]) == 1) continue;
				ok = true;
				break;
			}
			if (!ok) {
				cout << -1 << endl;
				return;
			}
			swap(v[i+1], v[k]);
			m.push_back(make_pair(i+2, k+1));
			swap(v[k], v[i]);
			m.push_back(make_pair(k+1, i+1));
			if (k < i) {
				swap(v[i+1], v[k]);
				m.push_back(make_pair(i+2, k+1));
			}
		} else {
			for (int j = i + 1; j < v.size(); ++j) {
				if (v[j] == i + 1) {
					swap(v[i], v[j]);
					m.push_back(make_pair(i+1, j+1));
				}
			}
		}
		if (m.size() > 5 * v.size()) {
			cout << -1 << endl;
			return;
		}
	}
	cout << m.size() << endl;
	for (auto &p : m) {
		cout << p.first << " " << p.second << endl;
	}
}

int main()
{
	int t;
	cin >> t;
	for (int i = 0; i < t; ++i) {
		int n;
		cin >> n;
		vector<int> v(n);
		for (int a = 0; a < n; ++a) {
			cin >> v[a];
		}
		solve(v);
	}
}

Test 1

Group: 1, 2

Verdict: WRONG ANSWER

Test 2

Group: 2

Verdict: WRONG ANSWER