advent2025

commit 3637ea9d48f67da86ae03baa0f31aa9ae6e54781
parent 514810dad8832a71be788e671fa8f6311374e5a0
Author: bsandro <email@bsandro.tech>
Date:   Wed, 10 Dec 2025 23:28:47 +0200

day10 p1 somehow works, I misread the task. Plenty of room to optimize too - gotta redo it with bit masks

Diffstat:
M
day10.c
 | 
99
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++--------------

1 file changed, 82 insertions(+), 17 deletions(-)
diff --git a/day10.c b/day10.c
@@ -1,5 +1,8 @@
 #include <stdio.h>
 #include <stdbool.h>
+#include <limits.h>
+#include <inttypes.h>
+#include "cputime.h"
 
 #define BUF_SIZE 256
 
@@ -10,38 +13,87 @@ typedef struct {
 
 typedef struct {
     int lights_l;
-    bool lights[16];
+    bool lights[16]; //@todo bit field? desired value
+    bool lights1[16];//overall value that we can change
     int buttons_l;
     Button buttons[16];
+    int presses;
 } Machine;
 
-void m_add_lights(Machine *m, int buf_l, char buf[buf_l]) {
+void m_lights_add(Machine *m, int buf_l, char buf[buf_l]) {
     for (int i=0;i<buf_l;++i) {
         m->lights[m->lights_l++] = buf[i]=='#';
     }
 }
 
-void m_add_button(Machine *m, int buf_l, char buf[buf_l]) {
+void m_button_add(Machine *m, int buf_l, char buf[buf_l]) {
     Button *btn = &m->buttons[m->buttons_l++];
     for (int i=0;i<buf_l;++i) {
         btn->toggles[btn->toggles_l++] = buf[i]-'0';
     }
 }
 
-void m_print(Machine *m, bool btns) {
-    puts("---- Machine ----");
-    printf("Lights:  [");
-    for (int i=0;i<m->lights_l;++i) printf("%c", m->lights[i]?'#':'.');
+bool m_lights_on(Machine *m) {
+    for (int i=0;i<m->lights_l;++i) {
+        if (m->lights[i]!=m->lights1[i]) return false;
+    }
+    return true;
+}
+
+void m_light_toggle(Machine *m, int light) {
+    m->lights1[light] = !m->lights1[light];
+}
+
+void m_print(Machine *m) {
+    printf("(%zu) Lights:  [", sizeof(Machine));
+    for (int i=0;i<m->lights_l;++i) printf("%c", m->lights1[i]?'#':'.');
     printf("]\n");
-    if (!btns) return;
-    printf("Buttons: ");
+}
+
+void m_btn_press(Machine *m, int b) {
+    Button *btn = &m->buttons[b];
+    for (int i=0;i<btn->toggles_l;++i) {
+        m_light_toggle(m, btn->toggles[i]);
+    }
+    m->presses++;
+}
+
+void m_btn_press_many(Machine *m, int comb_l, int comb[comb_l]) {
+    for (int i=0;i<comb_l;++i) {
+        m_btn_press(m, comb[i]);
+    }
+}
+
+bool try_combination(Machine *m, int comb_l, int comb[comb_l], int p) {
+    if (p==comb_l) {
+        /*printf("combination: ");
+        for (int i=0;i<comb_l;++i) printf("%d", comb[i]);
+        printf("\n");*/
+        Machine m1 = *m;
+        //m_print(&m1);
+        m_btn_press_many(&m1, comb_l, comb);
+        //puts("after:");
+        //m_print(&m1);
+        if (m_lights_on(&m1)) {
+            puts("ok");
+            return true;
+        }
+        //return m_lights_on(&m1);
+        return false;
+    }
     for (int i=0;i<m->buttons_l;++i) {
-        printf("(");
-        Button *btn = &m->buttons[i];
-        for (int j=0;j<btn->toggles_l;++j) printf("%d", btn->toggles[j]);
-        printf(") ");
+        if (p>0&&comb[p-1]==i) continue; // do not press same button twice in a row
+        comb[p] = i;
+        if (try_combination(m, comb_l, comb, p+1)) {
+            return true;
+        }
     }
-    printf("\n");
+    return false;
+}
+
+bool m_try_start(Machine m, int max_presses) {
+    int comb[max_presses];
+    return try_combination(&m, max_presses, comb, 0);
 }
 
 int main(void) {
@@ -51,11 +103,11 @@ int main(void) {
     int buf_l = 0;
     for (int c=getchar();c!=EOF;c=getchar()) {
         if (c==']') {
-            m_add_lights(&machines[machines_l], buf_l, buf);
+            m_lights_add(&machines[machines_l], buf_l, buf);
             buf_l = 0;
         }
         else if (c==')') {
-            m_add_button(&machines[machines_l], buf_l, buf);
+            m_button_add(&machines[machines_l], buf_l, buf);
             buf_l = 0;
         }
         else if ((c>='0'&&c<='9')||c=='.'||c=='#') buf[buf_l++] = c;
@@ -64,8 +116,21 @@ int main(void) {
             buf_l = 0;
         }
     }
+    int64_t part1 = 0;
+    int64_t part2 = 0;
     for (int i=0;i<machines_l;++i) {
-        m_print(&machines[i], false);
+        printf("---- Machine %p ----\n", &machines[i]);
+        printf("%d buttons\n", machines[i].buttons_l);
+        m_print(&machines[i]);
+        for (int j=1;j<=20;++j) {
+            printf("try start %i with %d button presses\n", i, j);
+            if (m_try_start(machines[i], j)) {
+                printf("%d presses start ok\n", j);
+                part1 += j;
+                break;
+            }
+        }
     }
+    printf("p1: %"PRIi64"\np2: %"PRIi64"\n", part1, part2);
     return 0;
 }