advent2019

commit 537e8e9ebfd79fdc0cba37596e75c57c12012403
parent a15787646c702afe8d9f9808d2c943992e1f7c36
Author: bsandro <email@bsandro.tech>
Date:   Fri, 26 Dec 2025 01:52:27 +0200

day03 p2

Diffstat:
M
day03.c
 | 
76
+++++++++++++++++++++++++++++++++++++++++-----------------------------------

1 file changed, 41 insertions(+), 35 deletions(-)
diff --git a/day03.c b/day03.c
@@ -15,6 +15,7 @@ typedef struct {
 
 typedef struct {
     Vec2 p1, p2;
+    int len;
 } Line;
 
 typedef struct {
@@ -37,45 +38,32 @@ Line normalize(Line l) {
     return l;
 }
 
-bool get_intersection(Line * restrict l1, Line * restrict l2, Vec2 * restrict p) {
-    (void)p;
-    if (l1->p1.x==l1->p2.x) { // l1 vertical
-        if (l2->p1.x==l2->p2.x) return false; // l2 is vertical too
-        if (l1->p1.x>l2->p1.x && l1->p2.x<l2->p2.x &&
-            l2->p1.y>l1->p1.y && l2->p2.y<l1->p2.y) {
-            p->x = l1->p1.x;
-            p->y = l2->p1.y;
+bool get_intersection(Line * restrict l1, Line * restrict l2, Vec2 * restrict p, int64_t * restrict steps) {
+    (void)steps;
+    Line ln1 = normalize(*l1);
+    Line ln2 = normalize(*l2);
+    if (ln1.p1.x==ln1.p2.x) { // ln1 vertical
+        if (ln2.p1.x==ln2.p2.x) return false; // ln2 is vertical too
+        if (ln1.p1.x>ln2.p1.x && ln1.p2.x<ln2.p2.x &&
+            ln2.p1.y>ln1.p1.y && ln2.p2.y<ln1.p2.y) {
+            p->x = ln1.p1.x;
+            p->y = ln2.p1.y;
+            *steps = abs(l1->p1.y - p->y) + abs(l2->p1.x - p->x);
             return true;
         }
-    } else if (l1->p1.y==l1->p2.y) { // l1 horizontal
-        if (l2->p1.y==l2->p2.y) return false; // l2 is horizontal too
-        if (l2->p1.x>l1->p1.x && l2->p2.x<l1->p2.x &&
-            l1->p1.y>l2->p1.y && l1->p2.y<l2->p2.y) {
-            p->x = l2->p1.x;
-            p->y = l1->p1.y;
+    } else if (ln1.p1.y==ln1.p2.y) { // ln1 horizontal
+        if (ln2.p1.y==ln2.p2.y) return false; // ln2 is horizontal too
+        if (ln2.p1.x>ln1.p1.x && ln2.p2.x<ln1.p2.x &&
+            ln1.p1.y>ln2.p1.y && ln1.p2.y<ln2.p2.y) {
+            p->x = ln2.p1.x;
+            p->y = ln1.p1.y;
+            *steps = abs(l1->p1.x - p->x) + abs(l2->p1.y - p->y);
             return true;
         }
     }
     return false;
 }
 
-int64_t calc_p1(Wire *w1, Wire *w2) {
-    int64_t r = -1;
-    for (int i=0;i<w1->len;++i) {
-        for (int j=0;j<w2->len;++j) {
-            Vec2 p = {0};
-            if (get_intersection(&w1->lines[i], &w2->lines[j], &p)) {
-                int dist = abs(p.x)+abs(p.y);
-                printf("intersection: {%d,%d}, dist: %d\n", p.x, p.y, dist);
-                if (r==-1) r = dist;
-                else if (dist<r) r = dist;
-            }
-        }
-    }
-    return r;
-}
-// 369 too low
-// 1167 too high
 int main(void) {
     Buffer buf = {0};
     Vec2 prev = {0};
@@ -92,7 +80,7 @@ int main(void) {
             else if (dir=='D') p.y -= dist;
             else if (dir=='L') p.x -= dist;
             else if (dir=='R') p.x += dist;
-            cw->lines[cw->len++] = normalize((Line){ .p1=prev, .p2=p });
+            cw->lines[cw->len++] = (Line){ .p1=prev, .p2=p, .len=dist };
             prev = p;
             if (c=='\n') {
                 cw = &w2;
@@ -105,9 +93,27 @@ int main(void) {
             buf.data[buf.len++] = c-'0';
         }
     }
-    int64_t p1 = calc_p1(&w1, &w2);
+    int64_t p1 = 0;
     int64_t p2 = 0;
-    printf("p1: %"PRIi64"\np2: %"PRIi64"\n", p1, p2);    
-    
+
+    int64_t steps1 = 0;
+    for (int i=0;i<w1.len;++i) {
+        int64_t steps2 = 0;
+        for (int j=0;j<w2.len;++j) {
+            Vec2 p = {0};
+            int64_t steps = 0;
+            if (get_intersection(&w1.lines[i], &w2.lines[j], &p, &steps)) {
+                int dist = abs(p.x)+abs(p.y);
+                if (p1==0) p1 = dist;
+                else if (dist<p1) p1 = dist;
+                int64_t steps_sum = steps1+steps2+steps;
+                if (p2==0) p2 = steps_sum;
+                else if (steps_sum<p2) p2 = steps_sum;
+            }
+            steps2 += w2.lines[j].len;
+        }
+        steps1 += w1.lines[i].len;
+    }
+    printf("p1: %"PRIi64"\np2: %"PRIi64"\n", p1, p2);
     return 0;
 }