From 9c999e9717b7e852ebe500572f0ba34b44c2f711 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/RESULTS.txt    |  8 ++++++
 2022/day06/aoc-c.c  | 60 +++++++++++++++++++++++++++++++++++++++++++++
 2022/day06/aoc.bash |  2 +-
 3 files changed, 69 insertions(+), 1 deletion(-)
 create mode 100644 2022/day06/aoc-c.c

diff --git a/2022/RESULTS.txt b/2022/RESULTS.txt
index 54fd0aa..d2c48ae 100644
--- a/2022/RESULTS.txt
+++ b/2022/RESULTS.txt
@@ -117,7 +117,15 @@ aoc.bash: res=1658
 	time: 0:00.06 real, 0.06 user, 0.00 sys
 	context-switch:	1+1, page-faults: 0+266
 
+aoc-c: res=1658
+	time: 0:00.00 real, 0.00 user, 0.00 sys
+	context-switch:	0+1, page-faults: 0+87
+
 +++++++++++++++++ part 2
 aoc.bash: res=2260
 	time: 0:00.09 real, 0.09 user, 0.00 sys
 	context-switch:	1+1, page-faults: 0+265
+
+aoc-c: res=2260
+	time: 0:00.00 real, 0.00 user, 0.00 sys
+	context-switch:	0+1, page-faults: 0+87
diff --git a/2022/day06/aoc-c.c b/2022/day06/aoc-c.c
new file mode 100644
index 0000000..6e5f228
--- /dev/null
+++ b/2022/day06/aoc-c.c
@@ -0,0 +1,60 @@
+/* aoc-c.c: Advent of Code 2022, day 6
+ *
+ * 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);
+}
diff --git a/2022/day06/aoc.bash b/2022/day06/aoc.bash
index f75a458..c149736 100755
--- a/2022/day06/aoc.bash
+++ b/2022/day06/aoc.bash
@@ -32,7 +32,7 @@ solve() {
         for ((j = 0; j < lcur; ++j)); do          # compare with previous ones
             if [[ $next == "${cur:j:1}" ]]; then  # duplicate
                 cur="${cur:j+1}$next"             # keep str after dup + new char
-                (( lcur = lcur - j ))
+                (( lcur -= j ))
                 continue 2
             fi
         done