aoc

commit 3aa3eb22370e3c6b2f47d47f451071497e0a2517
parent 7d62a62fd4da5f2b8ddb03efe5b99fba5e3709bb
Author: Sebastiano Tronto <sebastiano@tronto.net>
Date:   Sat, 23 Dec 2023 11:27:55 +0100

Added solution for 23

Diffstat:
A
2023/23/23a.c
 | 
38
++++++++++++++++++++++++++++++++++++++
A
2023/23/23b.c
 | 
97
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

2 files changed, 135 insertions(+), 0 deletions(-)
diff --git a/2023/23/23a.c b/2023/23/23a.c
@@ -0,0 +1,38 @@
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#define N 200
+
+bool v[N][N];
+char map[N][N];
+int n, s, t, sol;
+
+int max(int x, int y) { return x > y ? x : y; }
+
+int longpath(int i, int j) {
+	if (i == n-1 && j == t) return 0;
+	if (v[i][j]) return -1;
+
+	char c = map[i][j];
+	int ret = -1;
+	v[i][j] = true;
+	if (c == '.' || c == '>') ret = max(ret, longpath(i, j+1));
+	if (c == '.' || c == 'v') ret = max(ret, longpath(i+1, j));
+	if (c == '.' || c == '<') ret = max(ret, longpath(i, j-1));
+	if (c == '.' || c == '^') ret = max(ret, longpath(i-1, j));
+	v[i][j] = false;
+
+	return ret == -1 ? ret : ret + 1;
+}
+
+int main() {
+	for (n = 1; fgets(map[n], N, stdin) != NULL; n++) ;
+	memset(map[0], '#', n);
+	for (int i = 0; i < n; i++) if (map[1][i] == '.') s = i;
+	for (int i = 0; i < n; i++) if (map[n-1][i] == '.') t = i;
+
+	printf("%d\n", longpath(1, s));
+	return 0;
+}
diff --git a/2023/23/23b.c b/2023/23/23b.c
@@ -0,0 +1,97 @@
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#define N 150
+#define V 1000
+
+typedef struct { int i, j; } node_t;
+typedef struct { int u, w; } edge_t;
+int d[4][2] = {{1, 0}, {-1, 0}, {0, 1}, {0, -1}};
+
+bool v[N][N];
+char map[N][N];
+int n, s, t, nv, ne[V];
+node_t node[V];
+edge_t g[V][4];
+
+int max(int x, int y) { return x > y ? x : y; }
+
+bool isjunc(int i, int j) {
+	int nn = 0;
+	for (int k = 0; k < 4; k++)
+		nn += map[i+d[k][0]][j+d[k][1]] == '#';
+	return nn != 2;
+}
+
+void advance(int io, int jo, int *i, int *j) {
+	for (int k = 0; k < 4; k++) {
+		int ni = *i + d[k][0], nj = *j + d[k][1];
+		if (!v[ni][nj] && (ni != io || nj != jo) &&
+		    map[ni][nj] != '#') {
+			*i = ni;
+			*j = nj;
+			if (!isjunc(*i, *j)) v[*i][*j] = true;
+			return;
+		}
+	}
+}
+
+int findorcreate(int i, int j) {
+	for (int u = 0; u < nv; u++)
+		if (node[u].i == i && node[u].j == j)
+			return u;
+	node[nv] = (node_t) {.i = i, .j = j};
+	return nv++;
+}
+
+edge_t findedge(int io, int jo, int i, int j) {
+	int w;
+	v[i][j] = true;
+	for (w = 1; !isjunc(i, j); w++) advance(io, jo, &i, &j);
+	return (edge_t) {.u = findorcreate(i, j), .w = w};
+}
+
+void makegraph(int u) {
+	int i = node[u].i, j = node[u].j;
+	for (int k = 0; k < 4; k++) {
+		int ni = i + d[k][0], nj = j + d[k][1];
+		if (!v[ni][nj] && map[ni][nj] != '#') {
+			edge_t e = findedge(i, j, ni, nj);
+			g[u][ne[u]++] = (edge_t) {.u = e.u, .w = e.w};
+			g[e.u][ne[e.u]++] = (edge_t) {.u = u, .w = e.w};
+		}
+	}
+}
+
+int longpath(int u) {
+	int i = node[u].i, j = node[u].j, k, ret, p;
+
+	if (i == n-1 && j == t) return 0;
+	if (v[i][j]) return -1;
+
+	v[i][j] = true;
+	for (ret = -1, k = 0; k < ne[u]; k++)
+		if ((p = longpath(g[u][k].u)) != -1)
+			ret = max(ret, g[u][k].w + p);
+	v[i][j] = false;
+
+	return ret;
+}
+
+int main() {
+	for (n = 1; fgets(map[n], N, stdin) != NULL; n++) ;
+	memset(map[0], '#', n);
+	memset(map[n], '#', n);
+	for (int i = 0; i < n; i++) if (map[1][i] == '.') s = i;
+	for (int i = 0; i < n; i++) if (map[n-1][i] == '.') t = i;
+
+	findorcreate(1, s);
+	for (int u = 0; u < nv; u++)
+		makegraph(u);
+
+	printf("%d\n", longpath(0));
+
+	return 0;
+}