Queue Enqueue/Dequeue

Enqueue values at the back and dequeue them from the front in first-in, first-out order.

Algorithm

The replay uses the same three values in every language, so this C DSA implementation can be compared directly with the rest of the DSA track.

Basic Implementation

basic.c

#include <stdio.h>

void print_values(int values[], int count) {
    for (int i = 0; i < count; i++) {
        if (i > 0) printf(" -> ");
        printf("%d", values[i]);
    }
    printf("\n");
}

int main(void) {
    int queue[3];
    int front = 0;
    int back = 0;
    int removed[3];
    int count = 0;
    int values[] = {10, 20, 30};
    for (int i = 0; i < 3; i++) queue[back++] = values[i];
    while (front < back) removed[count++] = queue[front++];
    print_values(removed, count);
    return 0;
}

Complexity

Time: O(1) per operation with a real queue
Space: O(n)

Implementation notes

Keep the explicit stack/queue operations. Library shortcuts that only produce the final list hide the data-structure behavior this lesson is meant to replay.
The final output uses a deterministic a -> b -> c format for cross-language comparison.

front The front is the oldest value still waiting in the queue.

FIFO A queue removes values in first-in, first-out order.