Merkkijono

#include <iostream>
#include <string>

using namespace std;

int main() {
	string str;
	cin >> str;
	bool done = false;
	char lastChar = '\0';
	int i = 0;
	int start = 0;
	int end = 0;
	bool found = false;
	int size = 0;
	while (!done) {
		start = -1;
		end = 0;
		lastChar = '\0';
		found = false;
		size  = str.size();
		for (i = 0; i < size; i++) {
			char cur = str.at(i);
			if (cur == lastChar) {
				found = true;
				if (start == -1) {
					start = i - 1;
				}
				end = i;
			} else {
				if (start != -1) {
					end++;
					if (end >= size) {
						end = size - 1;
					}
					str.erase(str.begin() + start, str.begin() + end);
					start = -1;
				}
				lastChar = cur;
			}
		}
		if (!found) {
			done = true;
		}
	}
	cout << str;
	return 0;
}

Test 1

Verdict: ACCEPTED

Test 2

Verdict: RUNTIME ERROR

terminate called after throwing an instance of 'std::out_of_range'
  what():  basic_string::at

Test 3

Verdict: RUNTIME ERROR

terminate called after throwing an instance of 'std::out_of_range'
  what():  basic_string::at

Test 4

Verdict: RUNTIME ERROR

terminate called after throwing an instance of 'std::out_of_range'
  what():  basic_string::at

Test 5

Verdict: RUNTIME ERROR

terminate called after throwing an instance of 'std::out_of_range'
  what():  basic_string::at

Test 6

Verdict: RUNTIME ERROR

terminate called after throwing an instance of 'std::out_of_range'
  what():  basic_string::at

Test 7

Verdict: RUNTIME ERROR

terminate called after throwing an instance of 'std::out_of_range'
  what():  basic_string::at

Test 8

Verdict: RUNTIME ERROR

terminate called after throwing an instance of 'std::out_of_range'
  what():  basic_string::at

Test 9

Verdict: RUNTIME ERROR

terminate called after throwing an instance of 'std::out_of_range'
  what():  basic_string::at

Test 10

Verdict: RUNTIME ERROR

terminate called after throwing an instance of 'std::out_of_range'
  what():  basic_string::at