# Tideman PSET03 - Add_Pairs errors!

I'm currently doing the tideman pset and i have some errors on the add_pairs function and the lock_pais function but I'm more focused now on the add_pairs function. I don't know why these errors are happening. I'd like to know what they mean and why are happening. Please, help me on these problems: `:( add_pairs generates correct pair count when ties exist` and `:( add_pairs fills pairs array with winning pairs`. It'd be appreciated.

`add_pairs` function:

``````// Record pairs of candidates where one is preferred over the other
{
// TODO
// Iterating through the pairs array
bool theres_winner;
bool won;
int index;
int p;
do
{
index = pair_count;
won = false;
for (p = 0; p < candidate_count; p++)
{
// If the preferences is not 0
// If we have a winner:
if (pair_count != 0 && pairs[pair_count - 1].winner == 0 && pairs[pair_count - 1].loser == 0)
{
index = pair_count - 1;
}

theres_winner = (preferences[pair_count][p] > preferences[p][pair_count]);
alreadywon = ((pair_count == candidate_count - 1 || p != 0) && pairs[pair_count - 1].winner == pair_count && pairs[pair_count - 1].loser == p);

if (preferences[pair_count][p] != 0)
{
if ((preferences[pair_count][p] == preferences[p][pair_count]) || !theres_winner || alreadywon)
{
continue;
}

if (theres_winner)
{
// Assigning:
pairs[index].winner = pair_count;
pairs[index].loser = p;
pair_count++;
won = true;
break;
}
}
}

if (won != true)
{
pair_count++;
}

if (won == true && pair_count == candidate_count && preferences[pair_count - 1][p + 1] > preferences[p + 1][pair_count - 1])
{
pair_count--;
}
}
while (pair_count != candidate_count);
return;
}
``````

Tideman Code:

``````#include <cs50.h>
#include <stdio.h>
#include <strings.h>

// Max number of candidates
#define MAX 9

// preferences[i][j] is number of voters who prefer i over j
int preferences[MAX][MAX];

// locked[i][j] means i is locked in over j
bool locked[MAX][MAX];

// Each pair has a winner, loser
typedef struct
{
int winner;
int loser;
}
pair;

// Array of candidates
string candidates[MAX];
pair pairs[MAX * (MAX - 1) / 2];

int pair_count;
int candidate_count;

// Function prototypes
bool vote(int rank, string name, int ranks[]);
void record_preferences(int ranks[]);
void sort_pairs(void);
void lock_pairs(void);
void print_winner(void);

int main(int argc, string argv[])
{
// Check for invalid usage
if (argc < 2)
{
printf("Usage: tideman [candidate ...]\n");
return 1;
}

// Populate array of candidates
candidate_count = argc - 1;
if (candidate_count > MAX)
{
printf("Maximum number of candidates is %i\n", MAX);
return 2;
}
for (int i = 0; i < candidate_count; i++)
{
candidates[i] = argv[i + 1];
}

for (int f = 0; f < MAX; f++)
{
for (int k = 0; k < MAX; k++)
{
preferences[f][k] = 0;
}
}

// Clear graph of locked in pairs
for (int i = 0; i < candidate_count; i++)
{
for (int j = 0; j < candidate_count; j++)
{
locked[i][j] = false;
}
}

pair_count = 0;
int voter_count = get_int("Number of voters: ");

for (int i = 0; i < voter_count; i++)
{
// ranks[i] is voter's ith preference
int ranks[candidate_count];

// Query for each rank
for (int j = 0; j < candidate_count; j++)
{
string name = get_string("Rank %i: ", j + 1);

if (!vote(j, name, ranks))
{
printf("Invalid vote.\n");
return 3;
}
}

record_preferences(ranks);

printf("\n");
}

sort_pairs();
lock_pairs();
print_winner();
return 0;
}

// Update ranks given a new vote
bool vote(int rank, string name, int ranks[])
{
// TODO
// Iterating to check if the name is a valid cantidate, if so update the ranks array
for (int j = 0; j < candidate_count; j++)
{
//Comparing the name with a valid candidate and returning true
if (strcasecmp(name, candidates[j]) == 0)
{
// Checking the candidate has been voted
for (int f = rank - 1; f >= 0; f--)
{
if (ranks[f] == j)
{
return false;
}
}
ranks[rank] = j;
return true;
}
}
return false;
}

// Update preferences given one voter's ranks
void record_preferences(int ranks[])
{
// TODO
// Iterating trough each voters' ranks
for (int e = 0; e < candidate_count; e++)
{
for (int d = 0; d < candidate_count; d++)
{
// If comparing the same candidate, asign 0
if (ranks[e] == ranks[d])
{
preferences[ranks[e]][ranks[d]] = 0;
}
if (e < d)
{
preferences[ranks[e]][ranks[d]] = preferences[ranks[e]][ranks[d]] + 1;
}
}
}
return;
}

// Record pairs of candidates where one is preferred over the other
{
// TODO
// Iterating through the pairs array
bool theres_winner;
bool won;
int index;
int p;
do
{
index = pair_count;
won = false;
for (p = 0; p < candidate_count; p++)
{
// If the preferences is not 0
// If we have a winner:
if (pair_count != 0 && pairs[pair_count - 1].winner == 0 && pairs[pair_count - 1].loser == 0)
{
index = pair_count - 1;
}

theres_winner = (preferences[pair_count][p] > preferences[p][pair_count]);
alreadywon = ((pair_count == candidate_count - 1 || p != 0) && pairs[pair_count - 1].winner == pair_count && pairs[pair_count - 1].loser == p);

if (preferences[pair_count][p] != 0)
{
if ((preferences[pair_count][p] == preferences[p][pair_count]) || !theres_winner || alreadywon)
{
continue;
}

if (theres_winner)
{
// Assigning:
pairs[index].winner = pair_count;
pairs[index].loser = p;
pair_count++;
won = true;
break;
}
}
}

if (won != true)
{
pair_count++;
}

if (won == true && pair_count == candidate_count && preferences[pair_count - 1][p + 1] > preferences[p + 1][pair_count - 1])
{
pair_count--;
}
}
while (pair_count != candidate_count);
return;
}

// Sort pairs in decreasing order by strength of victory
void sort_pairs(void)
{
// TODO
int winner;
int loser;
int winner_next;
int loser_next;
pair tmp;
// Iterating through the pairs array
for (int h = 0; h < pair_count - 1; h++)
{
// Getting the winner and the loser of the 2 next pairs' values, if the first one has less strength of victory swap them (using bubble sort)
winner = pairs[h].winner;
loser = pairs[h].loser;
winner_next = pairs[h + 1].winner;
loser_next = pairs[h + 1].loser;
if (preferences[winner][loser] < preferences[winner_next][loser_next])
{
tmp = pairs[h];
pairs[h] = pairs[h + 1];
pairs[h + 1] = tmp;
}
}
return;
}

// Lock pairs into the candidate graph in order, without creating cycles
void lock_pairs(void)
{
// TODO
int winner;
int loser;
bool edge = false;
// Iterating trough the locked pairs
for (int v = 0; v < pair_count; v++)
{
// Getting the winner and loser
winner = pairs[v].winner;
loser = pairs[v].loser;
// Checking it it has a edge or not
if (v != pair_count - 1)
{
locked[winner][loser] = true;
}
else
{
for (int f = 0; f < pair_count; f++)
{
if (locked[loser][f] == true)
{
edge = true;
}
}

if (edge != true)
{
locked[winner][loser] = true;
}
}
}
return;
}

// Print the winner of the election
void print_winner(void)
{
// TODO
string winner;
bool no_winner[pair_count];
for (int t = 0; t < pair_count; t++)
{
no_winner[t] = false;
}

for (int l = 0; l < pair_count; l++)
{
for (int p = 0; p < pair_count; p++)
{
if (locked[p][l] == true)
{
no_winner[l] = true;
}
}
}

for (int w = 0; w < pair_count; w++)
{
if (no_winner[w] == false)
{
winner = candidates[w];
printf("%s\n", winner);
return;
}
}
}
``````