/* Function: modifyMap
 * -------------------
 * Modifies param frequenciesMap entries
 * for current char key.
 */
void modifyMap(MyMap<ext_char, int>& frequenciesMap,
               ext_char nextSymbol) {
    if (frequenciesMap.containsKey(nextSymbol)) {
        /* Modifies map entry - increments symbol value */
        int symbValue = frequenciesMap[nextSymbol];
        frequenciesMap.put(nextSymbol, ++symbValue);
    }else{
        /* Adds new map entry for this symbol */
        int symbApearence = 1;
        frequenciesMap.put(nextSymbol, symbApearence);
    }
}