day 6 part 1 (simple algorithm) + part 2 README

2021/day06/EXAMPLE.txt

@@ -1 +1 @@
-Initial state: 3,4,3,1,2
+3,4,3,1,2

2021/day06/README.txt

@@ -51,3 +51,14 @@ Each day, a 0 becomes a 6 and adds a new 8 to the end of the list, while each ot
 In this example, after 18 days, there are a total of 26 fish. After 80 days, there would be a total of 5934.
 
 Find a way to simulate lanternfish. How many lanternfish would there be after 80 days?
+
+Your puzzle answer was 362666.
+
+The first half of this puzzle is complete! It provides one gold star: *
+--- Part Two ---
+
+Suppose the lanternfish live forever and have unlimited food and space. Would they take over the entire ocean?
+
+After 256 days in the example above, there would be a total of 26984457539 lanternfish!
+
+How many lanternfish would there be after 256 days?

2021/day06/aoc-c.c

@@ -0,0 +1,142 @@
+/* aoc-c: Advent2021 game, day 6 parts 1 & 2
+ *
+ * Copyright (C) 2021 Bruno Raoult ("br")
+ * Licensed under the GNU General Public License v3.0 or later.
+ * Some rights reserved. See COPYING.
+ *
+ * You should have received a copy of the GNU General Public License along with this
+ * program. If not, see <https://www.gnu.org/licenses/gpl-3.0-standalone.html>.
+ *
+ * SPDX-License-Identifier: GPL-3.0-or-later <https://spdx.org/licenses/GPL-3.0-or-later.html>
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <string.h>
+#include <malloc.h>
+
+#include "debug.h"
+#include "bits.h"
+#include "list.h"
+#include "pool.h"
+
+typedef struct fish {
+    s16 value;
+    struct list_head list;
+} fish_t;
+
+static pool_t *pool;
+
+LIST_HEAD(fish_head);
+static int nfish=0;
+
+//#ifdef DEBUG
+static void print_fish()
+{
+    fish_t *fish;
+    int i = 0;
+
+    printf("fish # = %d\n", nfish);
+    list_for_each_entry(fish, &fish_head, list) {
+        printf("%s%d", i? ",":"", fish->value);
+        i++;
+    }
+    printf("\n");
+}
+//#endif
+
+static struct list_head *read_fish()
+{
+    char *buf, *token;
+    size_t alloc = 0;
+    fish_t *fish;
+
+    if (getline(&buf, &alloc, stdin) < 0)
+        return NULL;
+
+    if (!(pool = pool_init("fish", 1024, sizeof (struct fish))))
+        return NULL;
+
+    token = strtok(buf, ",\n");
+    while (token) {
+        //printf("token=[%s]\n", token);
+        if (!(fish = pool_get(pool)))
+            return NULL;
+        fish->value = atoi(token);
+        list_add_tail(&fish->list, &fish_head);
+        nfish ++;
+        token = strtok(NULL, ",\n");
+        //print_fish();
+    }
+    free(buf);
+    return &fish_head;
+}
+
+static int doit(int part)
+{
+    fish_t *fish, *new;
+    int toadd;
+    int iter = part == 1? 80: 256;
+
+    /* initial algorithm surely does not work for part 2:
+     * Too many memory allocation, nneed to rethink the whole...
+     *
+     */
+    for (; iter; --iter) {
+        //printf("iter = %2d: ", iter);
+        toadd = 0;
+        list_for_each_entry(fish, &fish_head, list) {
+            fish->value--;
+            if (fish->value < 0) {            /* was zero: create new fish */
+                fish->value = 6;
+                toadd++;
+                nfish++;
+            }
+        }
+        while (toadd--) {
+            if (!(new = pool_get(pool)))
+                return -1;
+            new->value = 8;
+            list_add_tail(&new->list, &fish_head);
+        }
+    }
+    return nfish;
+}
+
+static int usage(char *prg)
+{
+    fprintf(stderr, "Usage: %s [-d debug_level] [-p part]\n", prg);
+    return 1;
+}
+
+int main(int ac, char **av)
+{
+    int opt;
+    u32 exercise = 1, res;
+
+    while ((opt = getopt(ac, av, "d:p:")) != -1) {
+        switch (opt) {
+            case 'd':
+                debug_level_set(atoi(optarg));
+                break;
+            case 'p':                             /* 1 or 2 */
+                exercise = atoi(optarg);
+                if (exercise < 1 || exercise > 2)
+                    return usage(*av);
+                break;
+            default:
+                return usage(*av);
+        }
+    }
+    if (optind < ac)
+        return usage(*av);
+
+    read_fish();
+    print_fish();
+    res = doit(exercise);
+    //print_fish();
+    printf ("%s : res=%d\n", *av, res);
+    /* TODO: free board/mem pool */
+    exit (0);
+}