advent2025

commit 5820e9bd6310906b5f21b897da3182a893762a7c
parent 164d5e2fa652b528c8f0de1b41f4520a80bf620b
Author: bsandro <email@bsandro.tech>
Date:   Fri, 12 Dec 2025 00:55:31 +0200

day11 p2 works properly

Diffstat:
M
day11.c
 | 
51
++++++++++++++++++++++++++++-----------------------

1 file changed, 28 insertions(+), 23 deletions(-)
diff --git a/day11.c b/day11.c
@@ -9,6 +9,7 @@ Thing crashes pretty hard if 'svr'/'our' nodes weren't found, I don't care much.
 #include <strings.h>
 #include <stdbool.h>
 #include <stdlib.h>
+#include <inttypes.h>
 #include "cputime.h"
 
 #define NAME_LEN 4
@@ -67,8 +68,8 @@ int find_or_create(Nodes *nodes, char name[4]) {
 int bfs(Nodes *nodes) {
     int num = 0;
     int start = find_index(nodes, "you");
-    if (start==-1) return -1;
     int end = find_index(nodes, "out");
+    if (start==-1||end==-1) return -1;
     int queue[MAX_NODES] = {0};
     int front = 0;
     int back = 0;
@@ -85,38 +86,42 @@ int bfs(Nodes *nodes) {
     return num;
 }
 
-int dfs_walk(Nodes *nodes, int idx, int out, int dac, int fft) {
-    if (idx==out) {
-        for (int i=0;i<nodes->cnt;++i) if (nodes->nodes[i].visited) printf("-> %3d ",i);
-        printf("\n");
-        if (nodes->nodes[dac].visited&&nodes->nodes[fft].visited) return 1;
-        else return 0;
-    }
+int64_t dfs_walk(Nodes *nodes, int idx, int out) {
     Node *n = &nodes->nodes[idx];
-    n->visited = true;
+    if (idx==out) return 1;
     if (n->dead) return 0;
-    int num = 0;
+    n->visited = true;
+    int64_t num = 0;
     for (int i=0;i<n->adj_l;++i) {
         if (nodes->nodes[n->adj[i]].visited) continue;
-        //if (nodes->nodes[n->adj[i]].dead) continue;
-        num += dfs_walk(nodes, n->adj[i], out, dac, fft);
+        num += dfs_walk(nodes, n->adj[i], out);
     }
     n->visited = false;
-    if (num==0) n->dead = true;
+    if (num==0) {
+        n->dead = true;
+    }
     return num;
 }
 
-int dfs(Nodes *nodes) {
+int64_t dfs(Nodes *nodes, int from, int to) {
     int num = 0;
+    for (int i=0;i<nodes->nodes[from].adj_l;++i) {
+        num += dfs_walk(nodes, nodes->nodes[from].adj[i], to);
+    }
+    for (int i=0;i<nodes->cnt;++i) nodes->nodes[i].dead = false;
+    return num;
+}
+// svr -> fft -> dac -> out; dac never connects to fft
+int64_t part2(Nodes *nodes) {
+    int svr = find_index(nodes, "svr");
     int out = find_index(nodes, "out");
     int dac = find_index(nodes, "dac");
     int fft = find_index(nodes, "fft");
-    Node *start = find(nodes, "svr");
-    if (start==NULL) return -1;
-    for (int i=0;i<start->adj_l;++i) {
-        num += dfs_walk(nodes, start->adj[i], out, dac, fft);
-    }
-    return num;
+    if (svr==-1||out==-1||dac==-1||fft==-1) return -1;
+    int64_t n1 = dfs(nodes, svr, fft);
+    int64_t n2 = dfs(nodes, fft, dac);
+    int64_t n3 = dfs(nodes, dac, out);
+    return n1*n2*n3;
 }
 
 int main(void) {
@@ -138,8 +143,8 @@ int main(void) {
     }
 
     int p1 = bfs(nodes);
-    int p2 = dfs(nodes);
-    printf("p1: %d\np2: %d\n", p1, p2);
+    int64_t p2 = part2(nodes);
+    printf("p1: %d\np2: %"PRIi64"\n", p1, p2);
     return 0;
 }
-// 18
+// 15380569 too low