Vaihdot

input/code.cpp: In function 'bool is_sorted(std::vector<int>&)':
input/code.cpp:31:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for (int i = 1; i < v.size(); i++) {
                  ~~^~~~~~~~~~

#include <stdio.h> // include before iostream for faster scanf
#include <iostream>
#include <vector>
#include <string>
#include <map>
#include <unordered_map>
#include <algorithm>
#include <utility>
#include <set>
#include <unordered_set>
#include <cmath>
#include <math.h>
#include <queue>
#include <stdlib.h>
#include <string.h>
#include <sstream>
#include <tuple>
#include <utility>
#include <iomanip>
#include <iterator>

using namespace std;
typedef long long LL;

#define printv(printVec) for (auto printVecIter : (printVec)) cout << printVecIter << " "; cout << endl;

// g++ -Wall -Wshadow -std=c++11 a.cpp && ./a.out


bool is_sorted(vector<int> & v) {
	for (int i = 1; i < v.size(); i++) {
		if (v[i] < v[i-1]) return false;
	}
	return true;
}

int main() {
	std::ios::sync_with_stdio(false);cin.tie(0);
	int t; cin>>t;
	while (t--) {
		int n; cin>>n;
		vector<int> ans(n);
		for (int i =0;i<n;i++) {
			cin>>ans[i];
		}
		if (ans.size() <= 2) {
			if (is_sorted(ans)) {
				cout << 0 << "\n";
			} else {
				cout << -1 << "\n";
			}
			continue;
		}
		if (ans.size() == 3) {
			if (!is_sorted(ans)) {
				swap(ans[0], ans[2]);
				if (is_sorted(ans)) {
					cout << 1 << "\n";
					cout << 1 << " " << 3 << "\n";
				} else {
					cout << -1 << "\n";
				}
			} else {
				cout << 0 << "\n";
			}
			continue;
		}
		vector<pair<int,int>> ops;
		for (int i = 0; i < n; i++) {
			int idx = i+1;
			printv(ans);
			if (ans[i] == i + 1) continue; // already in place
			while (ans[idx] != i+1) idx++;
			bool swapFirst = true;
			if (i == 0 || i == 1) {
				swapFirst = false;
			}
			if (swapFirst) {
				ops.push_back({i+1, 1});
				ops.push_back({1, idx+1});
				swap(ans[i], ans[idx]);
			} else {
				ops.push_back({i+1, n});
				if (idx != n-1) {
					ops.push_back({n, idx+1});
				}
				swap(ans[i], ans[idx]);
			}
		}
		cout << ops.size() << "\n";
		for (auto p : ops) {
			cout << p.first << " " << p.second << "\n";
		}
	}
}

Test 1

Group: 1, 2

Verdict: WRONG ANSWER

Test 2

Group: 2

Verdict: WRONG ANSWER