From 9f01f4fee428243cfc2da9399f71c57ce02ff815 Mon Sep 17 00:00:00 2001
From: Bruno Raoult <braoult@gmail.com>
Date: Fri, 9 Dec 2022 16:24:13 +0100
Subject: [PATCH] 2022 day 6: C (parts 1 and 2)

---
 2022/day06/aoc-c.c | 60 ++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 60 insertions(+)
 create mode 100644 2022/day06/aoc-c.c

diff --git a/2022/day06/aoc-c.c b/2022/day06/aoc-c.c
new file mode 100644
index 0000000..9b1d840
--- /dev/null
+++ b/2022/day06/aoc-c.c
@@ -0,0 +1,60 @@
+/* aoc-c.c: Advent of Code 2022, day 5
+ *
+ * Copyright (C) 2022 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 <string.h>
+
+#include "br.h"
+#include "aoc.h"
+
+struct msg {
+    char *data;
+    size_t len;
+};
+
+static struct msg *parse(struct msg *msg)
+{
+    size_t alloc = 0;
+
+    msg->data=NULL;
+    msg->len = getline(&msg->data, &alloc, stdin);
+    msg->data[--msg->len] = 0;
+    return msg;
+}
+
+static int solve(struct msg *msg, int marklen)
+{
+    char *pcur = msg->data, *pnext = pcur;
+    int len = msg->len, lmark = 0;
+
+    for (; pnext < msg->data + len && lmark < marklen; lmark = ++pnext - pcur) {
+        for (int j = 0; j < lmark; ++j) {         /* compare with prev marker chars */
+            if (*(pcur+j) == *pnext) {            /* check new char with cur marker */
+                pcur += j + 1;                    /* move marker to after dup char */
+                goto nextchar;
+            }
+        }
+    nextchar: ;
+    }
+    return pnext - msg->data;
+}
+
+int main(int ac, char **av)
+{
+    int part = parseargs(ac, av);
+    struct msg msg;
+
+    printf("%s: res=%d\n", *av, solve(parse(&msg), part == 1? 4:14));
+    free(msg.data);
+    exit(0);
+}