Parsing a string as fast as possible that is using comma delimiters
There is no way to go under \$O(N)\$, just because you need to inspect the whole string.
The test if (stringToBeParsed.size() &gt; 0) does not speed up the execution; you may safely omit it.
quoteTriggered = quoteTriggered ? false : true; is a long way to say quoteTriggered = !quoteTriggered.
In

    if (quoteTriggered) {
        temporary.push_back(stringToBeParsed[i]);
    }   
    else {
        //place quote in to the temporary string and store it.
        temporary.push_back(stringToBeParsed[i]);
    }   


the character is pushed anyway, so testing for quoteTriggered is pointless.
The remaining flow in the loop can be streamlined as:

    if quoteIsTriggered or char_is_not_separator
        push_to_temporary
    else
        substring is parsed

Upon the loop termination, you don't need to inspect the last character - if it was comma, temporary will be conveniently empty. Just push temporary and be done.


Putting it all together:

    void parse(vector&lt;string&gt;&amp; inboundVector, const string&amp; stringToBeParsed, bool quotesUsed, const char&amp; charToSepBy)
    {
        string temporary = "";
        bool quoteTriggered = false;
        for (size_t i = 0; i &lt; stringToBeParsed.size(); i++) {
            if (stringToBeParsed[i] == '\"' &amp;&amp; quotesUsed) {
                quoteTriggered = !quoteTriggered;
                temporary.push_back(stringToBeParsed[i]);
                continue;
            }

            if (quoteTriggered || stringToBeParsed[i] != charToSepBy) {
                temporary.push_back(stringToBeParsed[i]);
            } else {
                inboundVector.push_back(temporary);
                temporary = "";
            }
        }

        inboundVector.push_back(temporary);
    }