Merkkijono

#include <iostream>
#include <string>

using namespace std;

int main()
{
	string input = "";
	cin >> input;

	bool modifyDone = false, modified = false, deleteNext = false;
	string output = "";
	char lastChar = ' ';
	while (!modifyDone)
	{
		lastChar = ' ';
		output = "";
		deleteNext = false;
		modified = false;
		for (unsigned int i = 0; i < input.length(); i++)
		{
			if (i != 0)
			{
				if (input[i] == lastChar && (!modified || deleteNext))
				{
					if (!deleteNext)
					{
						output.pop_back();
						deleteNext = true;
						modified = true;
					}
				}
				else
				{
					deleteNext = false;
					output += input[i];
					lastChar = input[i];
				}
			}
			else
			{
				lastChar = input[i];
				output += input[i];
			}
		}
		if (!modified || output.length() <= 0)
		{
			modifyDone = true;
		}
		else
		{
			input = output;
		}
	}
	cout << output << "\n";

	int a;
	cin >> a;

	return 0;
}

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