비슷한 코드의 프로그램인데 C++가 자바보다 느립니다

bool updateCandidateLists(int cellIndex, int candidateIndex)
{	
	game[cellIndex] = candidateLists[cellIndex][candidateIndex];
	candidateLists[cellIndex].clear();
 
	for (int i = 0; i < N * 3 - n * 2 - 1; i++) {
		int neighbor = neighborLists[cellIndex][i];
 
        if (game[neighbor] == '.') {
			vector<char>::iterator iter = candidateLists[neighbor].begin();
			vector<char>::iterator end = candidateLists[neighbor].end();
			iter = find(iter, end, game[cellIndex]);
			if (iter != end) {
				candidateLists[neighbor].erase(iter);
			}
 
			if (candidateLists[neighbor].empty()) {
                return false;
            }
        }
    }
    return true;
}