Remove special characters from String on C++

normalizing_chars_sample.cpp

#include <iostream>
#include <string>
#include <bits/stdc++.h>

std::string normalizeString(const std::string &input)
    {
        std::string output = "";
        std::string validChars = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZáãàâéêẽèíìîóôòõúù!@#$%^&*()_|+,.<>{}[]\\/-=?;:'\"   \n";
        std::string validUpper = "" + validChars;
        transform(validUpper.begin(), validUpper.end(), validUpper.begin(), ::toupper);
        std::string validLower = ""+validChars;
        transform(validChars.begin(), validChars.end(), validChars.begin(), ::tolower);
        for (int i=0; i<input.length(); i++) {
            std::cout << input[i] << "\n";
            if (validChars.find(input[i]) > validChars.length() &&
                validLower.find(input[i]) > validChars.length() &&
                validUpper.find(input[i]) > validUpper.length()) {
                continue;
            }
            output += input[i];
        }

        return output;
    }

int main() {
    std::cout << normalizeString("Hello, world! └");
    return 0;
}