Repository: TheAlgorithms/C-Plus-Plus
File: greedy_algorithms/gale_shapley.cpp (C++)

Code before:
                engagements[set_2_to_propose] = free_set_1;
                free_set_1_s[free_set_1] = false;
                free_set_1_s[currentFiance] = true;
            }
        }
    }

    std::cout << "Stable Matches:\n";
    for (int set_2 = 0; set_2 < n; set_2++) {
        std::cout << "set_2's " << set_2 << " is matched to set_1's " << engagements[set_2] << std::endl;
    }
    std::cout << std::endl;
}
}  // namespace stable_matching
}  // namespace greedy_algorithms

/**
 * @brief Self-test implementations
 * @returns void
 */

static void tests() {
    // Test Case 1
    std::vector<std::vector<int>> set_1_prefs = {{0, 1, 2, 3}, {2, 1, 3, 0}, {1, 2, 0, 3}, {3, 0, 1, 2}};
    std::vector<std::vector<int>> set_2_prefs = {{1, 0, 2, 3},{3, 0, 1, 2},{0, 2, 1, 3},{1, 2, 0, 3}};
    greedy_algorithms::stable_matching::gale_shapley(set_2_prefs, set_1_prefs);

    // Test Case 2
    set_1_prefs = {{0, 2, 1, 3}, {2, 3, 0, 1}, {3, 1, 2, 0}, {2, 1, 0, 3}};
    set_2_prefs = {{1, 0, 2, 3},{3, 0, 1, 2},{0, 2, 1, 3},{1, 2, 0, 3}};
    greedy_algorithms::stable_matching::gale_shapley(set_2_prefs, set_1_prefs);

    // Test Case 3
    set_1_prefs = {{0, 1, 2}, {2, 1, 0}, {1, 2, 0}};
    set_2_prefs = {{1, 0, 2},{2, 0, 1},{0, 2, 1}};
    greedy_algorithms::stable_matching::gale_shapley(set_2_prefs, set_1_prefs);
}

/**
 * @brief Main function
 * @returns 0 on exit
 */
int main() {
    tests(); // run self-test implementations
    return 0;
}


Review comment (suggestion):

this should be asserted to be a good value
that is 
```cpp
#include <cassert>
...
assert(1 == 1);
```

Code after:
            }
        }

        // If no free primary is found, break the loop
        if (free_primary_index == -1) break;

        // Get the next secondary to propose
        std::uint32_t secondary_to_propose = primary_preferences[free_primary_index][proposal_index[free_primary_index]];
        proposal_index[free_primary_index]++;

        // Get the current match of the secondary
        std::uint32_t current_match = matches[secondary_to_propose];

        // If the secondary is free, match them
        if (current_match == -1) {
            matches[secondary_to_propose] = free_primary_index;
            is_free_primary[free_primary_index] = false;
        } else {
            // Determine if the current match should be replaced
            auto new_proposer_rank = std::find(secondary_preferences[secondary_to_propose].begin(),
                                                secondary_preferences[secondary_to_propose].end(),
                                                free_primary_index);
            auto current_match_rank = std::find(secondary_preferences[secondary_to_propose].begin(),
                                                 secondary_preferences[secondary_to_propose].end(),
                                                 current_match);

            // If the new proposer is preferred over the current match
            if (new_proposer_rank < current_match_rank) {
                matches[secondary_to_propose] = free_primary_index;
                is_free_primary[free_primary_index] = false;
                is_free_primary[current_match] = true; // Current match is now free
            }
        }
    }

    return matches;
}
}  // namespace stable_matching
}  // namespace greedy_algorithms

/**
 * @brief Self-test implementations
 * @returns void
 */
static void tests() {
    // Test Case 1
    std::vector<std::vector<std::uint32_t>> primary_preferences = {{0, 1, 2, 3}, {2, 1, 3, 0}, {1, 2, 0, 3}, {3, 0, 1, 2}};
    std::vector<std::vector<std::uint32_t>> secondary_preferences = {{1, 0, 2, 3}, {3, 0, 1, 2}, {0, 2, 1, 3}, {1, 2, 0, 3}};
    assert(greedy_algorithms::stable_matching::gale_shapley(secondary_preferences, primary_preferences) == std::vector<std::uint32_t>({0, 2, 1, 3}));

    // Test Case 2