day 7 part 1 (C)

2021/day07/aoc-c.c

@@ -0,0 +1,147 @@
+/* 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"
+
+static int ncrabs, crab_grow, crab_alloc, crab_max;
+
+typedef struct crab {
+    int pos;
+    int ncrabs;
+} crab_t;
+
+crab_t *crabs = NULL;
+
+//#ifdef DEBUG
+static void print_crab()
+{
+    int i = 0;
+
+    printf("crabs=%d max=%d\n", ncrabs, crab_max);
+    for (i = 0; i < ncrabs; ++i)
+        printf("%s%d/%d", i? ", ": "", crabs[i].pos, crabs[i].ncrabs);
+    printf("\n");
+}
+//#endif
+
+static crab_t *grow_crabs()
+{
+    //static int crab_max = 0;
+    int old = crab_alloc;
+
+    crab_alloc += crab_grow;
+    crabs = realloc(crabs, crab_alloc * sizeof (*crabs));
+    for (int i = old; i < crab_alloc; ++i) {
+        crabs[i].pos = -1;
+        crabs[i].ncrabs = 0;
+    }
+    return crabs;
+}
+
+static int add_crab(int crab)
+{
+    int i;
+
+    if (crab > crab_max)
+        crab_max = crab;
+    if (ncrabs == crab_alloc)                     /* conservative grow */
+        grow_crabs();
+    for (i = 0; i < ncrabs; ++i) {
+        if (crabs[i].pos == crab) {
+            crabs[i].ncrabs++;
+            return i;
+        }
+    }
+    crabs[i].pos = crab;
+    crabs[i].ncrabs = 1;
+    ncrabs++;
+    return i;
+}
+
+static u64 read_crab()
+{
+    char *buf, *token;
+    size_t alloc = 0;
+    ssize_t length;
+
+    if ((length = getline(&buf, &alloc, stdin)) < 0)
+        return -1;
+    crab_grow = length / 2;
+
+    token = strtok(buf, ",\n");
+    while (token) {
+        add_crab(atoi(token));
+        token = strtok(NULL, ",\n");
+    }
+    free(buf);
+    return ncrabs;
+}
+
+static int doit(int part)
+{
+    int try, best_dist = 0, best_fuel = crab_max * crab_max;
+
+    if (part == 1) {
+        for (try = 0; try < crab_max; ++try) {
+            int fuel = 0;
+            for (int crab = 0; crab < ncrabs; ++crab)
+                fuel += abs(crabs[crab].pos - try) * crabs[crab].ncrabs;
+            if (fuel < best_fuel) {
+                best_dist = try;
+                best_fuel = fuel;
+            }
+        }
+    }
+    return best_fuel;
+}
+
+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;
+    int 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_crab();
+    res = doit(exercise);
+    printf ("%s : res=%d\n", *av, res);
+    exit (0);
+}