2020 day 22 part 1 (C)

2020/day22/aoc-c.c

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+/* aoc-c.c: Advent2020, day 22, part 1
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include <ctype.h>
+
+#include "list.h"
+#include "pool.h"
+#include "debug.h"
+
+struct card {
+    int card;
+    struct list_head list;
+};
+
+struct player {
+    int ncards;
+    struct list_head head;
+} players[2];
+
+pool_t *pool_cards;
+
+static void print_cards()
+{
+    struct card *card;
+    for (int player = 0; player < 2; ++player) {
+        log(2, "player %d (%d cards): ", player + 1, players[player].ncards);
+        list_for_each_entry(card, &players[player].head, list) {
+            log(2, "%d ", card->card);
+        }
+        log(2, "\n");
+    }
+}
+
+static void parse()
+{
+    size_t alloc;
+    ssize_t len;
+    char *buf = NULL;
+    int player = -1;
+    struct card *card;
+
+    INIT_LIST_HEAD(&players[0].head);
+    INIT_LIST_HEAD(&players[1].head);
+    players[0].ncards = players[1].ncards = 0;
+    while ((len = getline(&buf, &alloc, stdin)) > 0) {
+        buf[--len] = 0;
+        if (len == 0)
+            continue;
+        if (*buf == 'P') {
+            player++;
+            continue;
+        } else if (isdigit(*buf)) {               /* card */
+            card = pool_get(pool_cards);
+            card->card = atoi(buf);
+            players[player].ncards++;
+            list_add_tail(&card->list, &players[player].head);
+        }
+    }
+    free(buf);
+}
+
+static int usage(char *prg)
+{
+    fprintf(stderr, "Usage: %s [-d debug_level] [-p part]\n", prg);
+    return 1;
+}
+
+static long part1()
+{
+    struct card *c1, *c2;
+    int round = 0, mult = 1;
+    long res = 0;
+
+    while (players[0].ncards > 0 && players[1].ncards > 0) {
+        c1 = list_first_entry_or_null(&players[0].head, struct card, list);
+        c2 = list_first_entry_or_null(&players[1].head, struct card, list);
+        if (c1->card > c2->card) {
+            list_move_tail(&c1->list, &players[0].head);
+            list_move_tail(&c2->list, &players[0].head);
+            players[1].ncards--;
+            players[0].ncards++;
+        } else {
+            list_move_tail(&c2->list, &players[1].head);
+            list_move_tail(&c1->list, &players[1].head);
+            players[0].ncards--;
+            players[1].ncards++;
+        }
+        round++;
+        log(2, "\nafter round %d\n", round);
+        print_cards();
+    }
+    list_for_each_entry_reverse(c1,
+                                players[0].ncards? &players[0].head: &players[1].head,
+                                list) {
+        res += c1->card * mult++;
+    };
+    return res;
+}
+
+static long part2()
+{
+    return 2;
+}
+
+int main(ac, av)
+    int ac;
+    char **av;
+{
+    int opt, part = 1;
+
+    while ((opt = getopt(ac, av, "d:p:")) != -1) {
+        switch (opt) {
+            case 'd':
+                debug_level_set(atoi(optarg));
+                break;
+            case 'p':                             /* 1 or 2 */
+                part = atoi(optarg);
+                if (part < 1 || part > 2)
+            default:
+                    return usage(*av);
+        }
+    }
+
+    pool_cards = pool_create("cards", 128, sizeof(struct card));
+
+    parse();
+    print_cards();
+    printf("%s : res=%ld\n", *av, part == 1? part1(): part2());
+    exit (0);
+}