1 files changed, 43 insertions, 0 deletions

diff --git a/2023/04/4a.c b/2023/04/4a.c
new file mode 100644
index 0000000..a1f6a9e
--- /dev/null
+++ b/2023/04/4a.c
@@ -0,0 +1,43 @@
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#define N 1000
+
+bool isnum(char c) { return c >= '0' && c <= '9'; }
+
+int main() {
+        char *buf, line[N];
+        int i, j, x, sum, nw, nr, w[100], r[100];
+
+        sum = 0;
+        while ((buf = fgets(line, N, stdin)) != NULL) {
+                nr = nw = 0;
+                while (*buf != ':') buf++;
+                while (*buf != '|') {
+                        buf++;
+                        if (!isnum(*buf)) continue;
+                        w[nw++] = atoi(buf);
+                        while (isnum(*buf)) buf++;
+                }
+                while (*buf != '\n') {
+                        buf++;
+                        if (!isnum(*buf)) continue;
+                        r[nr++] = atoi(buf);
+                        while (isnum(*buf)) buf++;
+                }
+                for (x = 0, i = 0; i < nr; i++) {
+                        for (j = 0; j < nw; j++) {
+                                if (r[i] == w[j]) {
+                                        x++;
+                                        break;
+                                }
+                        }
+                }
+                sum += 1 << (x-1);
+        }
+
+        printf("%d\n", sum);
+        return 0;
+}