Demo Catch.hpp to test the function move all even numbers to left, all odd numbers to right

separateOddEven.cpp

#include <iostream>
#include <vector>

using namespace std;
#define CATCH_CONFIG_MAIN  // This tells Catch to provide a main() - only do this in one cpp file
#include "catch.hpp"
vector<int> separateOddEven(vector<int> arr) {
    auto left = arr.begin();
    auto right = arr.end() - 1;

    while (left < right) {
        if (*left % 2 == 0) {
            left++;
        } else if (*right % 2 == 0) {
            auto temp = *left;
            *left = *right;
            *right = temp;
        }

        if (*right % 2 == 1) {
            right--;
        }
    }

    return arr;
}

TEST_CASE("Separate Odd Event", "[separate]") {
    REQUIRE(separateOddEven({1, 2}) == vector<int>({2, 1}));
    REQUIRE(separateOddEven({1, 3, 2}) == vector<int>({2, 3, 1}));
    REQUIRE(separateOddEven({9, 10, 1, 2, 3, 4, 6, 8, 7, 12}) == vector<int>({12, 10, 8, 2, 6, 4, 3, 1, 7, 9}));
}