Cs50 Tideman Solution _verified_ 📥

The lock_pairs function builds the final graph by setting locked[i][j] = true .

My first instinct was to use a simple sorting algorithm (like bubble sort) on the pairs array. But I kept getting the order wrong. I was trying to sort the candidates themselves, rather than the magnitude of the margin .

Use make tideman and ./tideman [candidates] to test each function individually.

: Because of its difficulty, students are frequently warned that looking up a full "Tideman solution" is considered a violation of academic honesty . Cs50 Tideman Solution

After locking:

The Ranked Pairs method works by determining which candidate wins in head-to-head matchups. The algorithm follows a strict five-step process: Voters rank all candidates in order of preference.

The winner in a Tideman election is the "source" of the graph. The lock_pairs function builds the final graph by

: Updates a 2D array, preferences[i][j] , which tracks how many voters prefer candidate i over candidate j . 2. Identifying Winners ( add_pairs )

The winner is the candidate who has no locked edges pointing to them (i.e., no column in that row has a true value in the locked table).

To check for a cycle, you must write a recursive helper function (typically called has_cycle ). This function checks if the current loser can trace a path back to the current winner through already locked edges. I was trying to sort the candidates themselves,

void sort_pairs(void) { for (int i = 0; i < pair_count - 1; i++) { for (int j = 0; j < pair_count - i - 1; j++) { // Compare margins: pairs[j] vs pairs[j+1] int margin1 = preferences[pairs[j].winner][pairs[j].loser] - preferences[pairs[j].loser][pairs[j].winner]; int margin2 = preferences[pairs[j+1].winner][pairs[j+1].loser] - preferences[pairs[j+1].loser][pairs[j+1].winner]; if (margin1 < margin2) { // Swap pairs pair temp = pairs[j]; pairs[j] = pairs[j+1]; pairs[j+1] = temp; } } } } Use code with caution. 5. lock_pairs Function (The Hardest Part)

def update_preferences(pairs, eliminated_candidate): updated_pairs = [] for pair in pairs: updated_pair = [preference for preference in pair if preference != eliminated_candidate] updated_pairs.append(updated_pair) return updated_pairs

: The preferences[i][j] 2D array represents the number of voters who prefer candidate i over candidate j .

If you want, I can:

This is the most complex phase. The program iterates through the sorted pairs and "locks" them into a directed graph (using a locked[i][j] boolean matrix).