Sorting an array replaces values with zeros - c

Question

The problem starts near the very bottom of the array. I print percent[x] values to make sure they are there, and then after the sort, three of them are filled with zeros. I've been looking around for awhile but I can't find anything.
#include <stdio.h>
int main()
{
int votes[5][4]={192,48,206,37,
147,90,312,21,
186,12,121,38,
114,21,408,39,
267,13,382,29};
char cand[4]={'A','B','C','D'};
int row_totals[5];
int col_totals[4]; //This is left for you to do
//see code below to see how
//row_totals were calculated.
int total_votes;
//use a for loop to calculate
//using either row_totals or col_totals
float percent[4]; //use a for loop to calculate based on
int swap; //total_votes and col_totals
//be sure to print the totals for the candidates
//at the end, you will need to sort the percent array
//bringing along the values from the cand array. That is
//if a swap is made in the percent array, do the same
//swap in the cand array.
//then if percent[3] is greater than 50, declare cand[3] the winner
//if percent[3] is not greater than 50, declare a run-off
//between cand[2] and cand[3]
int row,col;
for(row=0;row<=4;row++) // used to find the row total
{
row_totals[row]=0;
for(col=0;col<=3;col++)
{
row_totals[row] += votes[row][col];
}
}
for(col=0; col <=3; col++)
{
col_totals[col]=0;
for(row =0; row <= 4; row++) // used to find the column total
{
col_totals[col] += votes[row][col];
}
}
for(row =0; row<=4; row++)
{
total_votes += row_totals[row]; //finds the total amount of the votes
}
printf(" Candidate Candidate Candidate Candidate Total\n");
printf(" Precinct: A B C D Votes\n");
for(row=0;row<=4;row++)
{
printf("%6d",row+1);
for(col=0;col<=3;col++)
{
printf("%12d",votes[row][col]);
}
printf("%11d\n",row_totals[row]);
}
printf("Total\nVotes:");
for(col=0; col<=3; col++)
{
printf("%12d", col_totals[col]);
}
printf(" %d", total_votes);
printf("\nPrecentage:");
for(col=0; col <= 3; col++)
{
percent[col] = (col_totals[col] / (double)total_votes); //calculates percentages
printf("%11f", percent[col]);
}
int x,y;
for(x=0; x<=3; x++)
{
printf("\n%f", percent[x]);
}
for(x=0; x<3; x++)
{
for(y=0;y<(3-x); y++)
{
if(percent[y] > percent[y+1])
{
swap = percent[y];
percent[y] = percent[y+1];
percent[y+1]= swap;
}
}
}
for(col=0; col<4; col++)
{
printf("\n%f", percent[col]);
}
return 0;

Answer 1

Your temporary variable for swapping is an integer, but the values you swap are floats between 0 and 1, which will become zero on conversion to int.
The error is hard to spot, because the temporary variable in declared at the top of the long main function, far away from the actual swapping code. You could make the temporary variable a local variable to the swapping scope:
for (x = 0; x < 3; x++) {
for (y = 0; y < (3 - x); y++) {
if (percent[y] > percent[y + 1]) {
float swap = percent[y];
percent[y] = percent[y + 1];
percent[y + 1] = swap;
}
}
}
Other issues:
Your total_votes isn't initialised to zero.
Please consider writing your loops as
for (row = 0; row < nrows; row++) ...
instead of
for (row = 0; row <= nrows - 1; row++) ...
This is a common C idiom. Your loops use hard-coded values, but later you might want to have variable limits as in the two examples above, where the "less than the number of items" variant is more readable.
When you print, new-lines should be at the end of your print formats, not at the beginning. This is the natural way of printing. It also has the benefit that the output buffer will be flushed when printing a newline to the console.
This is minor, but pick one floating-point type. You use float, but calculate your percentage with double. I recommend double, which is the standard floating-point type on modern machines.