From 6e09bb9bc428102d944e670aacb8eaa9b3ff53c4 Mon Sep 17 00:00:00 2001
From: Ian C <ianc@noddybox.co.uk>
Date: Sat, 25 Dec 2021 20:24:31 +0000
Subject: Added data for day 13.  Skeleton for day 12 but not sure how to
 approach it.

---
 12.c | 84 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 84 insertions(+)
 create mode 100644 12.c

(limited to '12.c')

diff --git a/12.c b/12.c
new file mode 100644
index 0000000..238b418
--- /dev/null
+++ b/12.c
@@ -0,0 +1,84 @@
+#include <stdlib.h>
+#include <stdio.h>
+#include <string.h>
+
+#define MAX_CONNECTIONS 50
+#define MAX_NODES       50
+
+typedef struct node
+{
+    char        name[32];
+    int         links;
+    struct node *link[MAX_CONNECTIONS];
+} Node;
+
+static Node node[MAX_NODES] = {0};
+static int nodes = 0;
+static Node *start = NULL;
+static Node *end = NULL;
+
+static char *ReadLine(char *p, size_t size, FILE *fp)
+{
+    if ((p=fgets(p, size, fp)))
+    {
+        size_t l = strlen(p);
+
+        while(l && p[l-1] == '\n')
+        {
+            p[--l] = 0;
+        }
+    }
+
+    return p;
+}
+
+static Node *GetOrAddNode(const char *name)
+{
+    int f;
+
+    for(f = 0; f < nodes; f++)
+    {
+        if (strcmp(name, node[f].name) == 0)
+        {
+            return node + f;
+        }
+    }
+
+    if (f == MAX_NODES)
+    {
+        fprintf(stderr, "Too many nodes\n");
+        exit(1);
+    }
+
+    strcpy(node[f].name, name);
+
+    return node + f;
+}
+
+static void Link(Node *node1, Node *node2)
+{
+    node1->link[node1->links++] = node2;
+    node2->link[node2->links++] = node1;
+}
+
+int main(void)
+{
+    char buff[4096];
+
+    start = GetOrAddNode("start");
+    end = GetOrAddNode("end");
+
+    while(ReadLine(buff, sizeof buff, stdin))
+    {
+        Node *node1, *node2;
+        char *p;
+
+        p = strtok(buff, "-");
+        node1 = GetOrAddNode(p);
+        p = strtok(NULL, "-");
+        node2 = GetOrAddNode(p);
+        Link(node1, node2);
+    }
+
+    return 0;
+}
-- 
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