How the "candidate" stuct is indexed in the following code?
When I try to print the last member(last index?) of the created struct which is candidates["last index"].name supposing I do have 4 candidates that will result the candidate_count which is = argc - 1 to equal to 4, so, I think if i accessed the 4th member by index of 4 I should reach the null terminator right? but that is not happening! the code looks like this
(Found at the end of the program)
printf("Winner is %s", candidates[4].name);
and It perfectly prints the 4th member name of the candidates name array! How is that? Shouldn't it be like
printf("Winner is %s", candidates[3].name)
Here is the full program I wrote:
#include <cs50.h>
#include <stdio.h>
#include <string.h>
#include <ctype.h>
// Max number of candidates
#define MAX 9 // define MAX as a constant = 9 (or any number which might be used without '=' sign).
// define syntax won't allocate any memory for the constant 'MAX', it can be used later as int MAX
// which = int 9
// Candidates have name and vote count, stuct is the best to use to create a custom data type.
typedef struct
{
string name;
int votes;
}
candidate;
// Array of candidates
candidate candidates[MAX];
// Number of candidates as a global variable
int candidate_count;
// Function prototypes
bool vote(string name);
void print_winner(void);
int main(int argc, string argv[])
{
// Check for invalid usage, the args. must be more than 2, i.e 3 and up!
if (argc < 2)
{
printf("Usage: plurality [candidate ...]\n");
return 1;
}
// Populate array of candidates
candidate_count = argc - 1; // -1 because one argument is the program's name. the rest are the
// candidates' names.
if (candidate_count > MAX)
{
printf("Maximum number of candidates is %i\n", MAX);
return 2; // err code 2 means that the candidates number is exceeded
}
for (int i = 0; i < candidate_count; i++) // Store the candidates names from the argv[] into,
// the struct candidate of candidates.name[] array to be globally available.
{
candidates[i].name = argv[i + 1]; // +1 because the 0th index is the programs name.
candidates[i].votes = 0; // initializing 0 for all candidates
}
// Enter the number of people allowed to vote, in other words, total number of votes allowed.
int voter_count = get_int("Number of voters: ");
// Loop over all voters to enter their votes for a candidate of the available names.
for (int i = 0; i < voter_count; i++)
{
string name = get_string("Vote: ");
// Check for invalid vote
if (!vote(name)) // Use function vote(string name) to check for the presence,
//of the candidate's name.
{
printf("Invalid vote.\n");
}
}
// Display winner of election
print_winner(); // call this func. to print the winner's name.
}
// Update vote totals given a new vote
bool vote(string name)
{ // loop over all candidates names checking it's availability by comparing it to user-entered name.
// global variable candidate_count is used to keep track of number of candidates.
for (int i = 0; i < candidate_count ; i++)
{
if (strcmp (name, candidates[i].name) == 0)
{
// Update the candidate's vote count.
candidates[i].votes++; // update the votes count for the candidate indexed @ i.
return true;
}
} // End for() iteration over the candidates names indeces.
return false;
}
// Print the winner (or winners) of the election
void print_winner(void)
/*
Bubble sorting Algorithm;
- A pass is a number of steps where the adjacent elements are compared to eachother from left to right in
an int array each one with the one next to it.
- If an array has a number of elements of 5, so, n = 5.
- There will always be a maximum of n - 1 passes in bubble sorting
- There will be a maximum of n - 1 comparisons of items in each pass if code is not optimized
*/
{
int swap = 0; // A flag to check if swapping happened.
//( To check if the array is sorted, swap happening = not sorted yet else the array is sorted)
for (int i = 0; i <= candidate_count - 1; i++) // passes = n - 1 where n = number of elements to compare.
{
for (int j = 0; j <= candidate_count - 1 - i; j++) // Number of comparisions(elements to be checked -
// with thier adjacent ones) to be conducted in each pass, after pass the last element will always
// be the greatest element there for no need to compare it with the element before it. therefore,
// candidate_count - 1 - i where i value starting form 0 by the outer for loop reduces the number -
// of steps or elements to be checked each iteration
{
/* if the first candidate number of votes element in the array is Greater-Than the adjacent next
one, swap them and keep a flag or indicate that you did swap them.
*/
if ( candidates[j].votes > candidates[j + 1].votes)
{
// Swap the position of the struct candidates elements inside
candidate temp = candidates[j];
candidates[j] = candidates[j + 1];
candidates[j + 1] = temp;
swap = 1; // a flag to indicated the swapping actually happened.
} // End swapping if() statement.
}
if (swap == 0) // if no swapping happened
break;
}
/* When Populating array of candidates, candidate_count = argc - 1; // -1 because one argument
is the program's name. the rest are the candidates' names.
*/
printf("Winner is %s, candidate count = %d \n", candidates[candidate_count].name, candidate_count);
return;
}
Copied from comments:
if I run the program in terminal and adding "printf"s to print candidates names & votes starting from index 0 to 5, that is what i am getting:
c ~/pset3/plurality/ $ ./plurality moh zoz sos
Number of voters: 5
Vote: moh
Vote: moh
Vote: moh
Vote: zoz
Vote: sos
Winner is moh, candidate count = 3
The candidate name : (null) votes : 0
The candidate name : zoz votes : 1
The candidate name : sos votes : 1
The candidate name : moh votes : 3
The candidate name : (null) votes : 0
The candidate name : (null) votes : 0
SOLUTION is just removing the 'equal to' from this line's condition:
for (int j = 0; j <= candidate_count - 1 - i; j++)
to look like this
for (int j = 0; j < candidate_count - 1 - i; j++)
