AoC18/day1p2/main.c

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

#include <glib.h>

/*
 * Apparently using a hash table for this is much faster...
 *
 * $ time ./main
 * 69285
 * ./main  271,27s user 0,11s system 99% cpu 4:33,04 total
 * $ time ./main_hash
 * 69285
 * ./main_hash  0,13s user 0,02s system 98% cpu 0,156 total
 */ 

#ifndef USE_HASH
gpointer g_array_lookup(GArray *array, gpointer item, guint size)
{
    for (gchar *i = array->data; i < array->data + array->len * size; i += size) {
        if (memcmp(i, item, size) == 0) {
            return i;
        }
    }
    return NULL;
}
#endif

int main()
{
    long value = 0;
    char *line = NULL;
    size_t line_len = 0;
    FILE *f = fopen("input", "r");
    if (!f) {
        perror("input");
        return 1;
    }

#ifdef USE_HASH
    GHashTable *hash = g_hash_table_new(g_direct_hash, g_direct_equal);
    g_hash_table_insert(hash, GINT_TO_POINTER(value), GINT_TO_POINTER(TRUE));
#else
    GArray *array = g_array_new(FALSE, FALSE, sizeof(long));
    g_array_append_val(array, value);
#endif

    while (1) {
        rewind(f);
        while (getline(&line, &line_len, f) != -1) {
            long number = strtol(line, NULL, 0);
            value += number;

#ifdef USE_HASH
            if (g_hash_table_lookup(hash, GINT_TO_POINTER(value))) goto found;
            g_hash_table_insert(hash, GINT_TO_POINTER(value), GINT_TO_POINTER(TRUE));
#else
            if (g_array_lookup(array, &value, sizeof(long))) goto found;
            g_array_append_val(array, value);
#endif
        }
    }
found:

    printf("%ld\n", value);

#ifdef USE_HASH
    g_hash_table_destroy(hash);
#else
    g_array_free(array, TRUE);
#endif
    free(line);
    fclose(f);
    return 0;
}