From: Mart Lubbers <mart@martlubbers.net>
Date: Sun, 5 Dec 2021 13:00:30 +0000 (+0100)
Subject: implement day 5 with hashmaps to gain a 20x speed increase
X-Git-Url: https://git.martlubbers.net/?a=commitdiff_plain;h=464433396dbb86c54b50aefa08b4ec188d82c609;p=advent21.git

implement day 5 with hashmaps to gain a 20x speed increase
---

diff --git a/05a.c b/05a.c
index 3e5b008..cdebe38 100644
--- a/05a.c
+++ b/05a.c
@@ -1,66 +1,54 @@
 #include <stdio.h>
-#include <stdlib.h>
-#include <stdbool.h>
+#include <uthash.h>
 
-struct line { enum {horz, vert} d; int x1; int y1; int x2; int y2; };
+#define SWAP(x, y) { x ^= y; y ^= x; x ^= y; }
 
-#define max(x, y) ((x)>(y) ? (x) : (y))
-#define min(x, y) ((x)<(y) ? (x) : (y))
-#define between(a, a1, a2) ((a) >= min(a1, a2) && (a) <= max(a1, a2))
+struct point { int x; int y; };
+struct entry { struct point key; int i; UT_hash_handle hh; };
 
-int parse_lines(struct line lines[], int *maxx, int *maxy)
+void mark_point(int x, int y, struct entry **entries, int *r)
 {
-	int i = 0;
-	char buf[1000];
-	while (fgets(buf, 1000, stdin) != NULL) {
-		char *p = &buf[0];
-		lines[i].x1 = strtol(p, &p, 10);
-		p++;
-		lines[i].y1 = strtol(p, &p, 10);
-		p+=4;
-		lines[i].x2 = strtol(p, &p, 10);
-		p++;
-		lines[i].y2 = strtol(p, &p, 10);
-		if (lines[i].x1 == lines[i].x2)
-			lines[i].d = vert;
-		else if (lines[i].y1 == lines[i].y2)
-			lines[i].d = horz;
-		else
-			continue;
-		*maxx = max(*maxx, lines[i].x1);
-		*maxx = max(*maxx, lines[i].x2);
-		*maxy = max(*maxy, lines[i].y1);
-		*maxy = max(*maxy, lines[i].y2);
-		i++;
+	struct entry *p;
+	struct point s = { .x=x, .y=y };
+	HASH_FIND(hh, *entries, &s, sizeof(struct point), p);
+	if (p) {
+		if (p->i++ == 1)
+			*r = *r+1;
+	} else {
+		p = malloc(sizeof(struct entry));
+		p->key = s;
+		p->i = 1;
+		HASH_ADD(hh, *entries, key, sizeof(struct point), p);
 	}
-	return i;
-}
-
-bool online(int x, int y, struct line line)
-{
-	switch (line.d) {
-	case vert:
-		return x == line.x1 && between(y, line.y1, line.y2);
-	case horz:
-		return y == line.y1 && between(x, line.x1, line.x2);
-	}
-	return false;
 }
 
 int main()
 {
-	struct line lines[1000];
-	int maxx = 0, maxy = 0;
-	int nlines = parse_lines(lines, &maxx, &maxy);
+	char buf[1000];
+	struct entry *entries = NULL;
 	int r = 0;
-	for (int x = 0; x<=maxx; x++) {
-		for (int y = 0; y<=maxy; y++) {
-			int matches = 0;
-			for (int line = 0; line<nlines && matches < 2; line++)
-				if (online(x, y, lines[line]))
-					matches++;
-			r = matches >= 2 ? r+1 : r;
-		}
+	while (fgets(buf, 1000, stdin) != NULL) {
+		char *ptr = &buf[0];
+		int x1 = strtol(ptr, &ptr, 10);
+		ptr++;
+		int y1 = strtol(ptr, &ptr, 10);
+		ptr+=4;
+		int x2 = strtol(ptr, &ptr, 10);
+		ptr++;
+		int y2 = strtol(ptr, &ptr, 10);
+		if (x1 > x2)
+			SWAP(x1, x2);
+		if (y1 > y2)
+			SWAP(y1, y2);
+
+		//Vertical
+		if (x1 == x2)
+			for (int y = y1; y<=y2; y++)
+				mark_point(x1, y, &entries, &r);
+		//Horizontal
+		else if (y1 == y2)
+			for (int x = x1; x<=x2; x++)
+				mark_point(x, y1, &entries, &r);
 	}
 	printf("%d\n", r);
 }
diff --git a/05b.c b/05b.c
index 208f870..f8dd141 100644
--- a/05b.c
+++ b/05b.c
@@ -1,72 +1,62 @@
 #include <stdio.h>
-#include <stdlib.h>
-#include <stdbool.h>
+#include <uthash.h>
 
-struct line { enum {horz, vert, diag} d; int x1; int y1; int x2; int y2; };
+#define SWAP(x, y) { x ^= y; y ^= x; x ^= y; }
 
-#define max(x, y) ((x)>(y) ? (x) : (y))
-#define min(x, y) ((x)<(y) ? (x) : (y))
-#define between(a, a1, a2) ((a) >= min(a1, a2) && (a) <= max(a1, a2))
+struct point { int x; int y; };
+struct entry { struct point key; int i; UT_hash_handle hh; };
 
-int parse_lines(struct line lines[], int *maxx, int *maxy)
+void mark_point(int x, int y, struct entry **entries, int *r)
 {
-	int i = 0;
-	char buf[1000];
-	while (fgets(buf, 1000, stdin) != NULL) {
-		char *p = &buf[0];
-		lines[i].x1 = strtol(p, &p, 10);
-		p++;
-		lines[i].y1 = strtol(p, &p, 10);
-		p+=4;
-		lines[i].x2 = strtol(p, &p, 10);
-		p++;
-		lines[i].y2 = strtol(p, &p, 10);
-		if (lines[i].x1 == lines[i].x2)
-			lines[i].d = vert;
-		else if (lines[i].y1 == lines[i].y2)
-			lines[i].d = horz;
-		else if (abs(lines[i].y2-lines[i].y1) == abs(lines[i].x2-lines[i].x1))
-			lines[i].d = diag;
-		else
-			continue;
-		*maxx = max(*maxx, lines[i].x1);
-		*maxx = max(*maxx, lines[i].x2);
-		*maxy = max(*maxy, lines[i].y1);
-		*maxy = max(*maxy, lines[i].y2);
-		i++;
+	struct entry *p;
+	struct point s = {.x=x, .y=y};
+	HASH_FIND(hh, *entries, &s, sizeof(struct point), p);
+	if (p) {
+		if (p->i++ == 1)
+			*r = *r+1;
+	} else {
+		p = malloc(sizeof(struct entry));
+		p->key = s;
+		p->i = 1;
+		HASH_ADD(hh, *entries, key, sizeof(struct point), p);
 	}
-	return i;
-}
-
-bool online(int x, int y, struct line line)
-{
-	int slope;
-	switch (line.d) {
-	case horz:
-		return y == line.y1 && between(x, line.x1, line.x2);
-	case vert:
-		return x == line.x1 && between(y, line.y1, line.y2);
-	case diag:
-		slope = (line.y2 - line.y1) / (line.x2 - line.x1);
-		return y-line.y1 == slope*(x-line.x1)
-			&& between(y, line.y1, line.y2) && between(x, line.x1, line.x2);
-	}
-	return false;
 }
 
 int main()
 {
-	struct line lines[1000];
-	int maxx = 0, maxy = 0;
-	int nlines = parse_lines(lines, &maxx, &maxy);
+	char buf[1000];
+	struct entry *entries = NULL;
 	int r = 0;
-	for (int x = 0; x<=maxx; x++) {
-		for (int y = 0; y<=maxy; y++) {
-			int matches = 0;
-			for (int line = 0; line<nlines && matches < 2; line++)
-				if (online(x, y, lines[line]))
-					matches++;
-			r = matches >= 2 ? r+1 : r;
+	while (fgets(buf, 1000, stdin) != NULL) {
+		char *ptr = &buf[0];
+		int x1 = strtol(ptr, &ptr, 10);
+		ptr++;
+		int y1 = strtol(ptr, &ptr, 10);
+		ptr+=4;
+		int x2 = strtol(ptr, &ptr, 10);
+		ptr++;
+		int y2 = strtol(ptr, &ptr, 10);
+
+		//Diagonal
+		if (abs(y2-y1) == abs(x2-x1)) {
+			int dx = x1 > x2 ? -1 : 1;
+			int dy = y1 > y2 ? -1 : 1;
+			for (; x1 != x2; x1 += dx, y1+= dy)
+				mark_point(x1, y1, &entries, &r);
+			mark_point(x1, y1, &entries, &r);
+		} else {
+			if (x1 > x2)
+				SWAP(x1, x2);
+			if (y1 > y2)
+				SWAP(y1, y2);
+			//Vertical
+			if (x1 == x2)
+				for (int y = y1; y<=y2; y++)
+					mark_point(x1, y, &entries, &r);
+			//Horizontal
+			else if (y1 == y2)
+				for (int x = x1; x<=x2; x++)
+					mark_point(x, y1, &entries, &r);
 		}
 	}
 	printf("%d\n", r);