Reverse Words in a String.cpp

class Solution {
public:
    string reverseWords(string s) {
        auto sourceSize = s.size();

	    string resultStr;
	    resultStr.reserve(sourceSize);

	    string str;
	    str.reserve(sourceSize / 2 );

	    auto concatStr = [](std::string &str1, std::string &str2)-> std::string {
		    if (str2.length() == 0)
			    return str1;

		    return str1 + " " + str2;
	    };

	    bool prevSymbol = false;

	    for (auto &c : s) {
		    bool isSpace = isspace(c) != 0;

		    if (isSpace && prevSymbol) {
			    resultStr = concatStr(str, resultStr);
			    str = "";
			    prevSymbol = false;
			    continue;
		    }
		    else if (isSpace)
		    {
		    	continue;
		    }

		    prevSymbol = true;
		    str += c;
	    }
	    if (str.length() != 0) {
	    	resultStr = concatStr(str, resultStr);
	    }


	    return resultStr;
    }


    void checkValue(string input, string expected)
    {
	    auto result = reverseWords(input);
	    if (result != expected) {
	    	throw new runtime_error("Failed on \"" + input + "\" Expected: " + expected);
	    }
    }
    
};