Hi, i have a problem with this code. ODD and EVEN numbers - c++

Question

I have a problem with this piece of code, I'm trying to print the EVEN and ODD numbers, but there is a problem when it comes to show them, the vectors don't save the numbers as I'm expecting.
#include <iostream>
using namespace std;
int main() {
int n;
cin >> n;
int vect[n], even[n], odd[n]; // CREATING VECTORS LIMIT AFTER "n"
for(int i = 1; i <= n; ++i) { // ENTERING The ELEMENS IN VECTOR
cin >> vect[i];
}
for(int i = 1; i <= n; ++i) {
if(vect[i] % 2 != 0) {
odd[i] = vect[i]; // I think that here's the problem, the vectors don't save the right numbers.
} /// VERIFYING IF THE NUMBER IS ODD OR EVEN.
else if (vect[i] % 2 == 0) {
even[i] == vect[i];
}
}
for(int i = 1; i <= n; ++i) {
cout << even[i] << " " << endl; /// PRINTING THE ODD AND EVEN numbers.
cout << odd[i] << " " << endl;
}
return 0;x
}

Answer 1

I have fixed the problem, thanks all for help.
Now it works perfectly.
#include <iostream>
using namespace std;
int main() {
int n;
cin >> n;
int vect[n], even[n], odd[n], z = 0, x = 0; // CREATING VECTORS LIMIT AFTER "n"
for(int i = 1; i <= n; ++i) { // ENTERING The ELEMENS IN VECTOR
cin >> vect[i];
}
for(int i = 1; i <= n; ++i) {
if(vect[i] % 2 != 0) {
odd[1+z] = vect[i];
z++;
// I think that here's the problem, the vectors don't save the right numbers.
} /// VERIFYING IF THE NUMBER IS ODD OR EVEN.
else if (vect[i] % 2 == 0) {
even[1+x] = vect[i];
x++;
}
}
for(int i = 1; i <= x; i++) {
cout << even[i] << " ";
}
cout << endl;
for(int i = 1; i <= z; i++) {
cout << odd[i] << " ";
}
return 0;
}

Answer 2

Considering the hints of the comments, your program shall be changed into this:
#include <iostream>
#include <vector>
using namespace std;
int main() {
int n, number;
cin >> n;
vector<int> vect, even, odd; // CREATING DYNAMIC VECTORS
for(int i = 0; i < n; ++i) { // ENTERING THE ELEMENTS IN VECTOR
cin >> number;
vect.push_back(number);
}
for(int i = 0; i < n; ++i) {
if(vect[i] % 2 != 0) { /// VERIFYING IF THE NUMBER IS ODD OR EVEN.
odd.push_back(vect[i]);
}
else {
even.push_back(vect[i]);
}
}
for (int i = 0; i < n; ++i)
cout << vect[i] << " ";
cout << endl;
/// PRINTING THE ODD AND EVEN NUMBERS.
for (auto& val : odd)
cout << val << " ";
cout << endl;
for (auto& val : even)
cout << val << " ";
cout << endl;
return 0;
}
It uses the vector container of STL for your arrays, start the indexing at 0 and prints out the resulting arrays separately, as the number of odd and of even entries might be different.
Hope it helps?

Answer 3

With standard, you might use std::partition (or stable version) to solve your problem:
void print_even_odd(std::vector<int> v)
{
auto limit = std::stable_partition(v.begin(), v.end(), [](int n){ return n % 2 == 0; });
std::cout << "Evens:";
// Pre-C++20 span:
// for (auto it = v.begin(); it != limit; ++it) { int n = *it;
for (int n : std::span(v.begin(), limit)) {
std::cout << " " << n;
}
std::cout << std::endl;
std::cout << "Odds:";
for (int n : std::span(limit, v.end())) {
std::cout << " " << n;
}
std::cout << std::endl;
}
Demo