Merkkijono

input/code.cpp: In function 'int main()':
input/code.cpp:21:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
    for (int z = 2; z <= w.size() - 2; z += 2) {
                    ~~^~~~~~~~~~~~~~~
input/code.cpp:27:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for (int x = 0; x < w.size(); x++) {
                  ~~^~~~~~~~~~

#include <vector>
#include <iostream>
#include <string>

using namespace std;

int main() {
	int n;
	cin >> n;
	
	vector<char> w;
	w.assign(1, 'a');
	w.resize(1);

	char lett[26]{'a','b','c','d','e','f','g','h','i','j','k','l','m','n','o','p','q','r','s','t','u','v','x','y','z'};

	for (int x = 0; x < n - 1; x++) {
		w.emplace(w.begin(), lett[x+1]);
		w.emplace(w.end(), lett[x+1]);
		if (x > 0) {
			for (int z = 2; z <= w.size() - 2; z += 2) {
				w.emplace(w.begin() + z, lett[x+1]);
			}
		}
	}
	string full;
	for (int x = 0; x < w.size(); x++) {
		full.push_back(w[x]);
	}
	cout << full << "\n";
}

Test 1

Verdict: ACCEPTED

Test 2

Verdict: ACCEPTED

Test 3

Verdict: ACCEPTED

Test 4

Verdict: ACCEPTED

Test 5

Verdict: ACCEPTED

Test 6

Verdict: ACCEPTED

Test 7

Verdict: ACCEPTED

Test 8

Verdict: ACCEPTED

Test 9

Verdict: ACCEPTED

Test 10

Verdict: ACCEPTED

Test 11

Verdict: ACCEPTED

Test 12

Verdict: ACCEPTED

Test 13

Verdict: ACCEPTED

Test 14

Verdict: ACCEPTED

Test 15

Verdict: ACCEPTED

Test 16

Verdict: ACCEPTED