# Tideman PSET03 - lock_pairs ERROR

I'm currently doing the Tideman PSET03 and I've completed almost everything except ``. Could you tell me why this is happening? It'd appreciated.

`lock_pairs` function code:

``````bool check_pair(int target, int loser)
{
// Loop through pairs
for (int i = 0; i < pair_count; i++)
{
// If this pair is locked:
if (locked[pairs[i].winner][pairs[i].loser] == true)
{
int pair_winner = pairs[i].winner;
int pair_loser = pairs[i].loser;
// Is there any pair with loser of the pair as a winner
if (loser == pair_winner)
{
// If yes, Is the loser of this pair equal to the target return true
if (pair_loser == target)
{
return true;
}
// If not call the recursive function and pass the new loser
else
{
return check_pair(target, pair_loser);
}
}
}
}

// If not makes a cycle return false
return false;
}

// Lock pairs into the candidate graph in order, without creating cycles
void lock_pairs(void)
{
// TODO
// Calling the recursive check_edge function
bool cycle;
for (int i = 0; i < pair_count; i++)
{
cycle = check_pair(pairs[i].winner, pairs[i].loser);

if (!cycle)
{
locked[pairs[i].winner][pairs[i].loser] = true;
}
}
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);
bool check_pair(int index_targer, int index_pair);
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 preferences array
for (int i = 0; i < candidate_count - 1; i++)
{
for (int j = i + 1; j < candidate_count; j++)
{
// If they are the same candidate continue the inner for loop otherwise asign their winners
if (preferences[i][j] == preferences[j][i])
{
continue;
}
else if (preferences[i][j] > preferences[j][i])
{
pairs[pair_count].winner = i;
pairs[pair_count].loser = j;
pair_count++;
}
else if (preferences[i][j] < preferences[j][i])
{
pairs[pair_count].winner = j;
pairs[pair_count].loser = i;
pair_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;
}

bool check_pair(int target, int loser)
{
// Loop through pairs
for (int i = 0; i < pair_count; i++)
{
// If this pair is locked:
if (locked[pairs[i].winner][pairs[i].loser] == true)
{
int pair_winner = pairs[i].winner;
int pair_loser = pairs[i].loser;
// Is there any pair with loser of the pair as a winner
if (loser == pair_winner)
{
// If yes, Is the loser of this pair equal to the target return true
if (pair_loser == target)
{
return true;
}
// If not call the recursive function and pass the new loser
else
{
return check_pair(target, pair_loser);
}
}
}
}

// If not makes a cycle return false
return false;
}

// Lock pairs into the candidate graph in order, without creating cycles
void lock_pairs(void)
{
// TODO
// Calling the recursive check_edge function
bool cycle;
for (int i = 0; i < pair_count; i++)
{
cycle = check_pair(pairs[i].winner, pairs[i].loser);

if (!cycle)
{
locked[pairs[i].winner][pairs[i].loser] = true;
}
}
return;
}

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

// Iterating through the locked array to get the possible winner of the election
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;
}
}
}

// If there is a false in the no_winner array that means is the winner of the election
for (int w = 0; w < pair_count; w++)
{
if (no_winner[w] == false)
{
winner = candidates[w];
printf("%s\n", winner);
return;
}
}
}
``````