Added solution for 20

1 files changed, 101 insertions, 0 deletions

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;
+}