From 5b8fcd4f166784bb43b09ef025b398875d13af5c Mon Sep 17 00:00:00 2001
From: Akuli <akuviljanen17@gmail.com>
Date: Sun, 5 Jan 2025 12:06:06 +0200
Subject: [PATCH] AoC 2024 day 23 (#544)

---
 examples/aoc2024/day23/part1.jou       |  89 ++++++++++++++++
 examples/aoc2024/day23/part2.jou       | 140 +++++++++++++++++++++++++
 examples/aoc2024/day23/sampleinput.txt |  32 ++++++
 3 files changed, 261 insertions(+)
 create mode 100644 examples/aoc2024/day23/part1.jou
 create mode 100644 examples/aoc2024/day23/part2.jou
 create mode 100644 examples/aoc2024/day23/sampleinput.txt

diff --git a/examples/aoc2024/day23/part1.jou b/examples/aoc2024/day23/part1.jou
new file mode 100644
index 00000000..ec4f23c7
--- /dev/null
+++ b/examples/aoc2024/day23/part1.jou
@@ -0,0 +1,89 @@
+import "stdlib/str.jou"
+import "stdlib/mem.jou"
+import "stdlib/io.jou"
+
+
+class Computer:
+    name: byte[3]
+    connections: void*[100]  # TODO: should be Computer*[100], can't be due to compiler bug
+
+    def connect(self, other: Computer*) -> None:
+        assert other != NULL
+
+        for i = 0; i < sizeof(self->connections)/sizeof(self->connections[0]); i++:
+            if self->connections[i] == NULL:
+                self->connections[i] = other
+                return
+
+        # array is full
+        assert False
+
+    def is_connected(self, other: Computer*) -> bool:
+        for i = 0; i < sizeof(self->connections)/sizeof(self->connections[0]); i++:
+            if self->connections[i] == other:
+                return True
+        return False
+
+
+def find_or_create_computer(computers: Computer*, ncomputers: int*, name: byte*) -> Computer*:
+    for i = 0; i < *ncomputers; i++:
+        if strcmp(computers[i].name, name) == 0:
+            return &computers[i]
+
+    c = &computers[*ncomputers]
+    assert strlen(name) == 2
+    strcpy(c->name, name)
+    memset(c->connections, 0, sizeof(c->connections))
+
+    ++*ncomputers
+    return c
+
+
+def main() -> int:
+    computers: Computer* = malloc(sizeof(computers[0]) * 5000)
+    assert computers != NULL
+    ncomputers = 0
+
+    f = fopen("sampleinput.txt", "r")
+    assert f != NULL
+    name1: byte[3]
+    name2: byte[3]
+
+    while fscanf(f, "%2s-%2s\n", name1, name2) == 2:
+        assert ncomputers < 5000
+        c1 = find_or_create_computer(computers, &ncomputers, name1)
+        assert ncomputers < 5000
+        c2 = find_or_create_computer(computers, &ncomputers, name2)
+        c1->connect(c2)
+        c2->connect(c1)
+
+    fclose(f)
+    printf("Got %d computers\n", ncomputers)  # Output: Got 16 computers
+
+    n = 0
+    for i = 0; i < ncomputers; i++:
+        for j = i+1; j < ncomputers; j++:
+            if i == j or not computers[i].is_connected(&computers[j]):
+                continue
+
+            for k = j+1; k < ncomputers; k++:
+                if (
+                    k == i
+                    or k == j
+                    or not computers[k].is_connected(&computers[i])
+                    or not computers[k].is_connected(&computers[j])
+                ):
+                    continue
+
+                if (
+                    computers[i].name[0] == 't'
+                    or computers[j].name[0] == 't'
+                    or computers[k].name[0] == 't'
+                ):
+                    # Found 3 connected
+                    n++
+
+    printf("%d\n", n)  # Output: 7
+
+    free(computers)
+    return 0
diff --git a/examples/aoc2024/day23/part2.jou b/examples/aoc2024/day23/part2.jou
new file mode 100644
index 00000000..ea50ff48
--- /dev/null
+++ b/examples/aoc2024/day23/part2.jou
@@ -0,0 +1,140 @@
+import "stdlib/str.jou"
+import "stdlib/mem.jou"
+import "stdlib/io.jou"
+
+
+def add_computer_if_not_exist(names: byte[3]*, ncomputers: int*, name: byte*) -> None:
+    for i = 0; i < *ncomputers; i++:
+        if strcmp(names[i], name) == 0:
+            return
+
+    assert strlen(name) == 2
+    strcpy(names[(*ncomputers)++], name)
+
+
+def find_computer(names: byte[3]*, ncomputers: int, name: byte*) -> int:
+    for i = 0; i < ncomputers; i++:
+        if strcmp(names[i], name) == 0:
+            return i
+    assert False
+
+
+# If conn_matrix[i][j] is True, then computers i and j are connected
+def create_conn_matrix(ncomputers: int) -> bool**:
+    conn_matrix: bool** = malloc(sizeof(conn_matrix[0]) * ncomputers)
+    assert conn_matrix != NULL
+
+    for i = 0; i < ncomputers; i++:
+        conn_matrix[i] = calloc(sizeof(conn_matrix[i][0]), ncomputers)
+        assert conn_matrix[i] != NULL
+
+    return conn_matrix
+
+
+def sort_names(names: byte[3]*, len: int) -> None:
+    # very dumb algorithm
+    while True:
+        did_something = False
+        for i = 1; i < len; i++:
+            if strcmp(names[i-1], names[i]) > 0:
+                memswap(&names[i-1], &names[i], sizeof(names[0]))
+                did_something = True
+        if not did_something:
+            break
+
+
+# recursive (depth-first search)
+def add_more_members_to_group(
+    group: int*,
+    group_len: int,
+    biggest_group: int*,
+    biggest_group_len: int*,
+    ncomputers: int,
+    conn_matrix: bool**,
+) -> None:
+    if group_len > *biggest_group_len:
+        *biggest_group_len = group_len
+        memcpy(biggest_group, group, sizeof(group[0]) * group_len)
+
+    # Always add members in order, speeds up search a lot
+    assert group_len > 0
+    for i = group[group_len - 1] + 1; i < ncomputers; i++:
+        # Do not add same group member twice.
+        # Do not add members that don't connect with all existing members.
+        ok = True
+        for k = 0; k < group_len; k++:
+            if not conn_matrix[i][group[k]]:
+                ok = False
+                break
+
+        if ok:
+            # Temporarily add new member to the group and recurse with it
+            group[group_len] = i
+            add_more_members_to_group(
+                group,
+                group_len + 1,
+                biggest_group,
+                biggest_group_len,
+                ncomputers,
+                conn_matrix,
+            )
+
+
+def main() -> int:
+    names: byte[3]* = malloc(sizeof(names[0]) * 5000)
+    assert names != NULL
+    ncomputers = 0
+
+    f = fopen("sampleinput.txt", "r")
+    assert f != NULL
+
+    name1: byte[3]
+    name2: byte[3]
+    while fscanf(f, "%2s-%2s\n", name1, name2) == 2:
+        assert ncomputers < 5000
+        add_computer_if_not_exist(names, &ncomputers, name1)
+        assert ncomputers < 5000
+        add_computer_if_not_exist(names, &ncomputers, name2)
+
+    sort_names(names, ncomputers)
+
+    rewind(f)
+    conn_matrix = create_conn_matrix(ncomputers)
+    while fscanf(f, "%2s-%2s\n", name1, name2) == 2:
+        i1 = find_computer(names, ncomputers, name1)
+        i2 = find_computer(names, ncomputers, name2)
+        conn_matrix[i1][i2] = True
+        conn_matrix[i2][i1] = True
+
+    fclose(f)
+
+    assert ncomputers < 5000
+    group: int[5000]
+    biggest_group: int[5000]
+    biggest_group_len = 0
+
+    for i = 0; i < ncomputers; i++:
+        group[0] = i
+        add_more_members_to_group(
+            group,
+            1,
+            biggest_group,
+            &biggest_group_len,
+            ncomputers,
+            conn_matrix,
+        )
+
+    # Output: co,de,ka,ta
+    for i = 0; i < biggest_group_len; i++:
+        if i != 0:
+            printf(",")
+        printf("%s", names[biggest_group[i]])
+    printf("\n")
+
+    for i = 0; i < ncomputers; i++:
+        free(conn_matrix[i])
+    free(conn_matrix)
+
+    free(names)
+
+    return 0
diff --git a/examples/aoc2024/day23/sampleinput.txt b/examples/aoc2024/day23/sampleinput.txt
new file mode 100644
index 00000000..3d497667
--- /dev/null
+++ b/examples/aoc2024/day23/sampleinput.txt
@@ -0,0 +1,32 @@
+kh-tc
+qp-kh
+de-cg
+ka-co
+yn-aq
+qp-ub
+cg-tb
+vc-aq
+tb-ka
+wh-tc
+yn-cg
+kh-ub
+ta-co
+de-co
+tc-td
+tb-wq
+wh-td
+ta-ka
+td-qp
+aq-cg
+wq-ub
+ub-vc
+de-ta
+wq-aq
+wq-vc
+wh-yn
+ka-de
+kh-ta
+co-tc
+wh-qp
+tb-vc
+td-yn