Järjestys

input/code.cpp: In function 'int main()':
input/code.cpp:67:34: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for (int i = 0; i < res.size(); ++i) {
                                  ^
input/code.cpp:69:31: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
         if (i != res.size() - 1) cout << " ";
                               ^

#include <iostream>
#include <vector>
#include <cmath>
// #include <fstream>
#include <algorithm>

using namespace std;

#define LSOne(S) (S & (-S))
typedef vector<int> vi;
typedef long long ll;

int n;

int pos[100005]; // ensimmäinen luku [1]
ll ft[100005]; // fenwick tree

vi res;

ll query(int b)	{
	ll sum = 0;
	for (; b; b -= LSOne(b)) sum += ft[b];
	return sum;
}

void update(int k, int v) {
	for (; k <= n; k += LSOne(k)) ft[k] += v;
}

void swap(int src, int dest) {
    if (src == dest) return;
    if (src == 1) {
        res.push_back(dest);
        res.push_back(dest - 1);
    }
    else {
        res.push_back(src);
        res.push_back(dest);
        res.push_back(dest - 1);
        res.push_back(src - 1);
    }
}

int main() {
    ios_base::sync_with_stdio(0);
    /*ifstream in("input.txt");
    cin.rdbuf(in.rdbuf());*/
    
    cin >> n;
    for (int i = 1; i <= n; ++i) {
        int cur;
        cin >> cur;
        pos[cur] = i;
        //cout << "pos[" << cur << "] = " << i << endl;
    }
    for (int i = n; i > 0; --i) {
        int src = pos[i] - query(pos[i]);
        // cout << "Number " << i << " is at " << src << endl;
        int dest = i;
        if (i == src) continue;
        // cout << "Swapping from " << src << " to " << dest << endl;
        swap(src, dest);
        update(pos[i] + 1, 1);
    }
        
    cout << res.size() << endl;
    for (int i = 0; i < res.size(); ++i) {
        cout << res[i];
        if (i != res.size() - 1) cout << " ";
    }          
    cout << endl;
    
    return 0;
}

Test 1

Group: 1

Verdict: ACCEPTED

Test 2

Group: 2

Verdict: ACCEPTED

Test 3

Group: 3

Verdict: ACCEPTED