advent2023

commit 5f889027bb1ee05d04ee549c8c05641f21c6e01e
parent 165d0e25020bdbad2c134ae4d0557eb01b8f209a
Author: bsandro <email@bsandro.tech>
Date:   Fri,  8 Dec 2023 18:25:39 +0200

day 08 p2 laptop transition commit

Diffstat:
M
day08/puzzle.c
 | 
64
++++++++++++++++++++++++++++++++++++++++++++++++++++++++--------

1 file changed, 56 insertions(+), 8 deletions(-)
diff --git a/day08/puzzle.c b/day08/puzzle.c
@@ -41,6 +41,20 @@ Node * find_node(Node *first, char name[4]) {
 	return NULL;
 }
 
+typedef struct Anode {
+	Node *start;
+	int znodes[];
+} Anode;
+
+bool check_z_nodes(Anode *anodes, size_t len) {
+	for (size_t i=0; i<len; ++i) {
+		if (anodes[i].start->name[2]!='Z') {
+			return false;
+		}
+	}
+	return true;
+}
+
 void print_nodes(Node *first) {
 	Node *node = first;
 	while (node!=NULL) {
@@ -61,6 +75,8 @@ void puzzle(const char *filename, long long *result1, long long *result2) {
 
 	Node *nodes = NULL;
 	Node *nodes_last = NULL;
+	Anode *anodes = NULL;
+	size_t anodes_len = 0;
 	const char *instructions = NULL;
 
 	while (fgets(buf, STR_LEN, infile) != NULL) {
@@ -79,6 +95,14 @@ void puzzle(const char *filename, long long *result1, long long *result2) {
 			if (nodes==NULL) nodes = node;
 			if (nodes_last!=NULL) nodes_last->next = node;
 			nodes_last = node;
+
+			// starting nodes for p.2
+			if (node->name[2]=='A') {
+				++anodes_len;
+				anodes = realloc(anodes, anodes_len*sizeof(Anode*));
+				anodes[anodes_len-1].start = node;
+				//anodes[anodes_len-1].znodes = NULL;
+			}
 		}
 		++line_num;
 		bzero(buf, STR_LEN);
@@ -86,18 +110,15 @@ void puzzle(const char *filename, long long *result1, long long *result2) {
 
 	int steps = 0;
 	int il = strlen(instructions);
+	// p.1
 	Node *n = find_node(nodes, "AAA");
 	while (1) {
 		char instr = instructions[steps % il];
-		Node *nn = NULL;
-		if (instr=='L') {
-			nn = find_node(nodes, n->left);
-		} else if (instr=='R') {
-			nn = find_node(nodes, n->right);
-		} else {
+		if (instr!='L'&&instr!='R') {
 			printf("illegal instruction %c\n", instr);
-			return;
+			break;
 		}
+		Node *nn = find_node(nodes, instr=='L'?n->left:n->right);
 		if (nn==NULL) {
 			printf("node %s was not found\n", instr=='L'?n->left:n->right);
 			break;
@@ -114,8 +135,35 @@ void puzzle(const char *filename, long long *result1, long long *result2) {
 		}
 	}
 
+	// p.2
+	steps = 0;
+	while (1) {
+		char instr = instructions[steps % il];
+		if (instr!='L'&&instr!='R') {
+			printf("illegal instruction %c\n", instr);
+			break;
+		}
+		for (size_t i=0; i<anodes_len; ++i) {
+			Node *n = anodes[i];
+			Node *nn = find_node(nodes, instr=='L'?n->left:n->right);
+			if (nn==NULL) {
+				printf("node %s was not found\n", instr=='L'?n->left:n->right);
+				return;
+			}
+			anodes[i] = nn;
+		}
+		++steps;
+		if (check_z_nodes(anodes, anodes_len)) {
+			*result2 = steps;
+			break;
+		}
+		if (steps==INT_MAX) {
+			printf("steps overflow\n");
+			break;
+		}
+	}
+
 	// mutiny! ignoring feof/ferror.
 	fclose(infile);
-	(void)result1;
 	(void)result2;
 }