advent2019

commit a15787646c702afe8d9f9808d2c943992e1f7c36
parent 9d237f29e03cd4ecb44b1760d5edc0f39bcb496d
Author: bsandro <email@bsandro.tech>
Date:   Fri, 26 Dec 2025 00:43:14 +0200

day03 p1

Diffstat:
A
day03.c
 | 
113
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

1 file changed, 113 insertions(+), 0 deletions(-)
diff --git a/day03.c b/day03.c
@@ -0,0 +1,113 @@
+#include <stdio.h>
+#include <inttypes.h>
+#include <stdbool.h>
+#include <stdlib.h>
+#include "cputime.h"
+
+typedef struct {
+    char data[8];
+    int len;
+} Buffer;
+
+typedef struct {
+    int x, y;
+} Vec2;
+
+typedef struct {
+    Vec2 p1, p2;
+} Line;
+
+typedef struct {
+    int len;
+    Line lines[512];
+} Wire;
+
+int btoi(Buffer buf) {
+    int num = 0;
+    for (int i=0;i<buf.len;++i) num = num*10+buf.data[i];
+    return num;
+}
+
+Line normalize(Line l) {
+    if (l.p1.x>l.p2.x || l.p1.y>l.p2.y) {
+        Vec2 t = l.p1;
+        l.p1 = l.p2;
+        l.p2 = t;
+    }
+    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;
+            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;
+            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};
+    Wire w1 = {0};
+    Wire w2 = {0};
+    Wire *cw = &w1;
+    char dir;
+    for (int c=getchar();c!=EOF;c=getchar()) {
+        if (c==','||c=='\n') {
+            int dist = btoi(buf);
+            buf.len = 0;
+            Vec2 p = prev;
+            if (dir=='U') p.y += dist;
+            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 });
+            prev = p;
+            if (c=='\n') {
+                cw = &w2;
+                prev.x = 0;
+                prev.y = 0;
+            }
+        } else if (c>='A'&&c<='Z') {
+            dir = c;
+        } else {
+            buf.data[buf.len++] = c-'0';
+        }
+    }
+    int64_t p1 = calc_p1(&w1, &w2);
+    int64_t p2 = 0;
+    printf("p1: %"PRIi64"\np2: %"PRIi64"\n", p1, p2);    
+    
+    return 0;
+}