Here we’ll see how to write C program to count occurrences of each element in an array. The C program will check how many times a particular integer occurs in the array.
#include <stdio.h>
#define MAX_ARRAY_LEN 1024
int main(){
int arr[MAX_ARRAY_LEN];
int counter[MAX_ARRAY_LEN];
int len = 0;
int i, j;
printf("Enter the array size: ");
scanf("%d", &len);
printf("Enter array elements: ");
for (i = 0; i < len; i++) {
scanf("%d", &arr[i]);
counter[i] = -1; /* Marking as not visisted. */
}
for (i = 0; i < len; i++) {
/* i-th element is already visited/counted. */
if (counter[i] == 0) continue;
counter[i] = 1;
for (j = i + 1; j < len; j++) {
if(arr[i] == arr[j]) {
counter[i]++;
counter[j] = 0;
}
}
}
for (i = 0; i < len; i++) {
if (counter[i] == 0) continue;
printf("%d occured %d times.\n", arr[i], counter[i]);
}
return 1;
}This program first takes the array size and the array elements as input. It maintains another array of same size to keep the elements counters / occurrences.
For each array element, the corresponding counter array element is initialized as -1 to mark as non-visited.
The outer loop iterates for every element of the array. If the corresponding counter [counter[i]] is 0 (means already visited), it skips that element. The inner loop scans the next array elements.
If a match is found, the corresponding counter array element is set to 0 to mark as visited. And the counter is incremented by 1.
At the element, for all elements with non-zero counter value is printed with their corresponding occurrence counter.
Here is sample output.
$ cc test.c -o test
$ ./test
Enter the array size: 10
Enter array elements: 2 32 5 45 6 2 2 45 32 32
2 occured 3 times.
32 occured 3 times.
5 occured 1 times.
45 occured 2 times.
6 occured 1 times.
