Random string from vector C++ [closed] - c++

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I have a question about this code. I got what I was expecting but I don't understand why sometimes I get the result and sometimes not.
In this case, the output suppose to show the word "dive" every time I run the code but sometimes the output is not giving me any value.
Is it because the if statement? How can I get always the result("dive") and not sometimes?
#include <iostream>
#include <string>
#include <vector>
#include <ctime>
using namespace std;
int main()
{
srand(time(NULL));
vector <string> Words = {"dive", "friends", "laptop"};
string n_words = Words[rand() % Words.size()];
for(int i = 0; i < 1; i++)
{
if(n_words.length() <= 4)
{
cout << n_words << endl;
}
}
}
EDIT ANOTHER EXAMPLE:
I would like to pick up a random word not longer than 4 letters from a list of words with differents lengths. When I run my code sometimes I get "dive" sometimes "lego" and sometimes nothing. Is there any way to get always some of this two values ?
#include <iostream>
#include <string>
#include <vector>
#include <ctime>
using namespace std;
int main()
{
srand(time(NULL));
vector <string> Words = {"dive", "table", "laptop", "lego", "friends"}
string n_words = Words[rand() % Words.size()];
for(int i = 0; i < 1; i++)
{
if(n_words.length() <= 4)
{
cout << n_words << endl;
}
}
}

Answer 1

Personally I would copy to a secondary temporary vector, shuffle it, and get the first element of that vector.
And I would have put it in a separate function.
In code something like this perhaps:
std::string select_random_short_word(std::vector<std::string> const& long_words)
{
// Create a vector and copy all "short" words to it
std::vector<std::string> short_words;
std::copy_if(begin(long_words), end(long_words), std::back_inserter(short_words),
[](std::string const& w) { return w.length() <= 4; });
// Make sure there are any short words
if (short_words.size() == 0)
{
return ""; // Nope, no short words
}
// Randomly shuffle the short words
std::random_device device;
std::default_random_engine engine(device());
std::shuffle(begin(short_words), end(short_words), engine);
// Return a random short word
return short_words[0];
}
This will reduce your main function to simply:
int main()
{
std::vector<std::string> words = {"dive", "table", "laptop", "lego", "friends"};
std::cout << select_random_short_word(words) << '\n';
}