From 477ed667b1a9bc7f73850f45449666a8907ecaed Mon Sep 17 00:00:00 2001
From: Sebastiano Tronto <sebastiano@tronto.net>
Date: Wed, 20 Dec 2023 16:32:41 +0100
Subject: Added solution for 20

---
 2023/20/20a.c | 101 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 101 insertions(+)
 create mode 100644 2023/20/20a.c

(limited to '2023/20/20a.c')

diff --git a/2023/20/20a.c b/2023/20/20a.c
new file mode 100644
index 0000000..99b6874
--- /dev/null
+++ b/2023/20/20a.c
@@ -0,0 +1,101 @@
+#include <inttypes.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#define N 100
+#define ischar(c) (c >= 'a' && c <= 'z')
+
+typedef struct {
+	int nin, nout, in[N], out[N];
+	char name[20], outc[N][20];
+	bool isff, ison, reg[N];
+} node_t;
+
+typedef struct {
+	int i, n, node[1000];
+	bool hi[1000];
+} queue_t;
+
+char *buf, line[N][N];
+int b, n;
+int64_t hitot, lowtot;
+node_t m[N];
+
+void add(queue_t *q, int v, bool hi) {
+	q->node[q->n] = v;
+	q->hi[q->n] = hi;
+	q->n++;
+}
+
+void send(queue_t *q, int v, bool hi) {
+	for (int j = 0; j < m[v].nout; j++) {
+		add(q, m[v].out[j], hi);
+		m[m[v].out[j]].reg[v] = hi;
+		if (hi) hitot++; else lowtot++;
+	}
+}
+
+void pushbutton(void) {
+	queue_t q = {0};
+
+	add(&q, b, false);
+	lowtot++;
+	while (q.i < q.n) {
+		int v = q.node[q.i];
+		bool hi = q.hi[q.i];
+		q.i++;
+
+		if (v == b) {
+			send(&q, v, hi);
+		} else if (m[v].isff) {
+			if (!hi)
+				send(&q, v, m[v].ison = !m[v].ison);
+		} else {
+			bool allhi = true;
+			for (int j = 0; j < m[v].nin; j++)
+				allhi = allhi && m[v].reg[m[v].in[j]];
+			send(&q, v, !allhi);
+		}
+	}
+}
+
+int main() {
+	for (n = 0; (buf = fgets(line[n], N, stdin)) != NULL; n++) {
+		if (ischar(*buf)) b = n;
+		m[n].isff = *buf == '%';
+		if (!ischar(*buf)) buf++;
+		for (int i = 0; ischar(*buf); m[n].name[i++] = *(buf++)) ;
+		buf += 4;
+		for (int i = 0; *buf != '\n'; i++) {
+			while (!ischar(*buf)) buf++;
+			for (int j = 0; ischar(*buf); m[n].outc[i][j++] = *(buf++)) ;
+		}
+	}
+
+	for (int i = 0; i < n; i++) {
+		for (int j = 0; m[i].outc[j][0]; j++) {
+			bool found = false;
+			for (int k = 0; k < n; k++) {
+				if (!strcmp(m[k].name, m[i].outc[j])) {
+					m[i].out[m[i].nout++] = k;
+					m[k].in[m[k].nin++] = i;
+					found = true;
+				}
+			}
+			if (!found) {
+				m[i].out[m[i].nout++] = n;
+				m[n].in[m[n].nin++] = i;
+				n++;
+			}
+		}
+	}
+
+	for (int i = 0; i < 1000; i++)
+		pushbutton();
+
+	printf("%" PRId64 " (%" PRId64 " low, %" PRId64 " hi)\n",
+	    hitot * lowtot, lowtot, hitot);
+	return 0;
+}
-- 
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