I have written this code in order to implement the Counting Sort in C. However it does not seem working properly. I create an array of 10 elements and then I apply the steps of counting sort. Basically it orders the first elements, and then as last elements it uses the last elements of the original array. I am not understanding where is the problem. The code:
#include <stdio.h>
#include <stdlib.h>
#include <time.h>
int main() {
// create an array of 100 random elements
// int my_array[10];
int my_array[] = { 10, 10, 9, 9, 6, 5, 4, 3, 2, 1 };
srand(time(NULL));
int i;
int N = 10;
/* for (i = 0; i < 10; i++) {
my_array[i] = rand() % 100 + 1;
} */
// print the array
for (i = 0; i < 10; i++) {
printf("%d\n", my_array[i]);
}
// define the minimum and the maximum as the first element of the array
int min_array = my_array[0];
int max_array = my_array[0];
printf("--------------\n");
// find the minimum and the maximum of the array
for (i = 0; i < N; i++) {
if (my_array[i] < min_array) {
min_array = my_array[i];
}
else if (my_array[i] > max_array) {
max_array = my_array[i];
}
}
// check if it worked
printf("max_array %d\n", max_array);
printf("min_array %d\n", min_array);
//
int range_array;
range_array = max_array - min_array + 1;
int count_array[range_array + 1];
for (i = 0; i < range_array; i++)
count_array[i] = 0;
int j = 0;
for (int i = 0; i < 10; i++) {
count_array[my_array[i] - min_array] = count_array[my_array[i] - min_array] + 1;
}
int z = 0;
for (i = min_array; i < max_array; i++) {
for (j = 0; j < count_array[i - min_array]; j++)
my_array[z++] = i;
// z = z + 1;
}
for (i = 0; i < N; i++) {
printf("%d\n", my_array[i]);
}
}
And one possible output:
10 10 9 9 6 5 4 3 2 1
--------------
max_array 10
min_array 1
--------------
1 2 3 4 5 6 9 9 2 1
So as you can see the numbers from 1 to 9 are ordered, while the last one, 10, is not ordered, and it uses the first numbers, so 1 and 2.
When rebuilding the array, you want to include the elements with a value of max_array
.
i<max_array
should be
i<=max_array
As a side note, you never use the last element of count_array
, so it should be one element smaller.
int count_array[range_array + 1];
should be
int count_array[range_array];
(Spotted by @user3386109)