createCharMap method
Implementation
List<List<Char>> createCharMap() {
final List<List<Char>> charMap = [[]];
for (int i = 0; i < chars.length; i++) {
charMap.last.add(chars[i]);
if (chars[i] == '\n') charMap.add([]);
}
charMap.last.add(eofStr);
return charMap;
}