From: Mart Lubbers <mart@martlubbers.net>
Date: Thu, 9 Dec 2021 14:37:18 +0000 (+0100)
Subject: without hashmaps
X-Git-Url: https://git.martlubbers.net/?a=commitdiff_plain;h=698a4470f15e440fea7583e77a97c541a83315f1;p=advent21.git

without hashmaps
---

diff --git a/09b.c b/09b.c
index 3db03bf..23b3a12 100644
--- a/09b.c
+++ b/09b.c
@@ -1,34 +1,15 @@
 #include <stdio.h>
-#include <stdlib.h>
 #include <string.h>
 #include <stdbool.h>
-#include <uthash.h>
+#include <stdint.h>
 
-struct point { int x; int y; };
-struct entry { struct point key; UT_hash_handle hh; };
+struct point { uint8_t x; uint8_t y; };
+bool visited[102][102] = {0};
+int grid[102][102];
 
-bool havevisited(struct entry **visited, int x, int y)
+int basin(int x, int y)
 {
-	struct entry *e = NULL;
-	struct point p;
-	memset(&p, 0, sizeof(p));
-	p.x = x;
-	p.y = y;
-	HASH_FIND(hh, *visited, &p, sizeof(struct point), e);
-	return e;
-}
-
-void addvisited(struct entry **visited, struct point p)
-{
-	struct entry *e = calloc(1, sizeof(struct entry));
-	e->key = p;
-	HASH_ADD(hh, *visited, key, sizeof(struct point), e);
-}
-
-int basin(struct entry **visited, int grid[102][102], int x, int y)
-{
-	struct point stack[1000];
-	memset(stack, 0, sizeof stack);
+	struct point stack[100];
 
 	int sp = 0;
 	int size = 0;
@@ -38,21 +19,21 @@ int basin(struct entry **visited, int grid[102][102], int x, int y)
 	memset(&p, 0, sizeof p);
 	while(--sp >= 0) {
 		p = stack[sp];
-		if (havevisited(visited, p.x, p.y))
+		if (visited[p.y][p.x])
 			continue;
-		addvisited(visited, p);
+		visited[p.y][p.x] = true;
 
 		if (grid[p.y][p.x] == 9)
 			continue;
 		size++;
 
-		if (!havevisited(visited, p.x+1, p.y))
+		if (!visited[p.y][p.x+1])
 			stack[sp++] = (struct point){.x=p.x+1, .y=p.y};
-		if (!havevisited(visited, p.x-1, p.y))
+		if (!visited[p.y][p.x-1])
 			stack[sp++] = (struct point){.x=p.x-1, .y=p.y};
-		if (!havevisited(visited, p.x, p.y+1))
+		if (!visited[p.y+1][p.x])
 			stack[sp++] = (struct point){.x=p.x, .y=p.y+1};
-		if (!havevisited(visited, p.x, p.y-1))
+		if (!visited[p.y-1][p.x])
 			stack[sp++] = (struct point){.x=p.x, .y=p.y-1};
 	}
 	return size;
@@ -60,7 +41,6 @@ int basin(struct entry **visited, int grid[102][102], int x, int y)
 
 int main()
 {
-	int grid[102][102];
 	for (int i = 0; i<102; i++)
 		for (int j = 0; j<102; j++)
 			grid[i][j] = 9;
@@ -78,11 +58,10 @@ int main()
 	}
 
 	int tl[3] = {0};
-	struct entry *visited = NULL;
 	for (int cy = 1; cy<y; cy++) {
 		for (int cx = 1; cx<maxx+1; cx++) {
-			if (!havevisited(&visited, cx, cy)) {
-				int s = basin(&visited, grid, cx, cy);
+			if (!visited[cy][cx]) {
+				int s = basin(cx, cy);
 				if (s >= tl[0]) {
 					tl[2] = tl[1];
 					tl[1] = tl[0];