Samozrejme, tu je upravený program v jazyku C:

```c
#include <stdio.h>
#include <stdlib.h>

#define FOOD_COUNT 5

struct snake {
    int x;
    int y;
    struct snake* next;
};

struct state {
    struct snake* snake;
    int foodx[FOOD_COUNT];
    int foody[FOOD_COUNT];
    int sx;
    int sy;
    int width;
    int height;
};

struct snake* add_snake(struct snake* snake, int x, int y) {
    struct snake* head = (struct snake*)malloc(sizeof(struct snake));
    if (head == NULL) {
        return NULL;
    }
    head->x = x;
    head->y = y;
    head->next = snake;
    return head;
}

struct snake* remove_snake(struct snake* snake) {
    if (snake == NULL) {
        return NULL;
    }
    struct snake* next = snake->next;
    free(snake);
    return next;
}

int is_snake(struct snake* snake, int x, int y) {
    while (snake != NULL) {
        if (snake->x == x && snake->y == y) {
            return 1;
        }
        snake = snake->next;
    }
    return 0;
}

void free_snake(struct snake* snake) {
    while (snake != NULL) {
        struct snake* next = snake->next;
        free(snake);
        snake = next;
    }
}

int main() {
    // Place your testing code here
    return 0;
}