Leimasin

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

int main(void)
{
	size_t n, m, k;
	std::cin >> n >> m >> k;

	std::string leimasin;
	std::cin >> leimasin;

	std::string mj = std::string(n, '.');
	std::vector<size_t> kohdat;
	kohdat.reserve(k);
	for (size_t i = 0; i < k; ++i)
	{
		size_t kohta;
		std::cin >> kohta;
		kohdat.push_back(kohta - 1);
	}

	// iterate backwards and never replace non-'.' chars
	for (size_t i = kohdat.size() - 1; i < kohdat.size(); --i)
	{
		for (size_t j = 0; j < m; ++j)
		{
			if (mj[kohdat[i] + j] == '.')
				mj[kohdat[i] + j] = leimasin[j];
		}
	}

	std::cout << mj << std::endl;
}

Test 1

Group: 1, 2, 3

Verdict: ACCEPTED

Test 2

Group: 1, 2, 3

Verdict: ACCEPTED

Test 3

Group: 1, 2, 3

Verdict: ACCEPTED

Test 4

Group: 1, 2, 3

Verdict: ACCEPTED

Test 5

Group: 2, 3

Verdict: ACCEPTED

Test 6

Group: 2, 3

Verdict: ACCEPTED

Test 7

Group: 2, 3

Verdict: ACCEPTED

Test 8

Group: 2, 3

Verdict: ACCEPTED

Test 9

Group: 3

Verdict: ACCEPTED

Test 10

Group: 3

Verdict: ACCEPTED

Test 11

Group: 3

Verdict: ACCEPTED

Test 12

Group: 3

Verdict: TIME LIMIT EXCEEDED

Test 13

Group: 3

Verdict: TIME LIMIT EXCEEDED

Test 14

Group: 3

Verdict: TIME LIMIT EXCEEDED