//小学生

std::string RemoveSpacesAndNewlines(char* input) {        //危险
	std::string out;                                    //多余
	for (long long i = 0; i < strlen(input); i++) {    //频繁strlen加难看
		if (input[i] != " " && input[i] != '\n') {    //不准确
			out = out  + ch;                         //多次内存开销，多余还难看
		}
	}
	return out;                                   //多次内存开销还多余
}
                                                //好像没一行看得过去

//高级小学生

std::string RemoveSpacesAndNewlines(const char* input/*防止误操*/) {
	std::string out;
	long long len = strlen(input);//减轻开销
	for (long long i = 0; i < len; i++) {
		if (input[i] != ' ' && input[i] != '\r' && input[i] != '\n') {
			out += ch;
		}
	}
	return out;
}

//普通

std::string RemoveSpacesAndNewlines(const std::string& input) {
	std::string out = "";
	for (char ch : input) {
		if (ch != ' ' && ch != '\n' && ch != '\r') {
			out += ch;
		}
	}
	return out;
}

//大神

void RemoveSpacesAndNewlines(const std::string& input, std::string& _out) {
    _out.clear();
	_out.reserve(input.size());
	for (char ch : input) {
		if (ch != ' ' && ch != '\n' && ch != '\r') {
			_out.append(ch);
		}
	}
}

大神代码中有一个致命BUG~~~

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