1 files changed, 66 insertions, 0 deletions

diff --git a/2023/03/3b.c b/2023/03/3b.c
new file mode 100644
index 0000000..27b5b7c
--- /dev/null
+++ b/2023/03/3b.c
@@ -0,0 +1,66 @@
+#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 grab(char *buf) {
+        int x;
+
+        if (!isnum(*buf))
+                return 0;
+
+        while (isnum(*buf)) buf--;
+        buf++;
+        x = atoi(buf);
+        while (isnum(*buf)) *buf++ = '.';
+
+        return x;
+}
+
+void push(int *j, int *g, char *buf) {
+        g[*j] = grab(buf);
+        if (g[*j] > 0) (*j)++;
+}
+
+int main() {
+        char *cont, line[N], prev[N], next[N], backup[3][N];
+        int i, sum, j, g[9];
+
+        sum = 0;
+        memset(line, '.', N);
+        memset(prev, '.', N);
+        memset(next, '.', N);
+        cont = fgets(&next[1], N-1, stdin);
+        while (cont != NULL) {
+                memcpy(line, next, N);
+                cont = fgets(&next[1], N-1, stdin);
+                for (i = 1; line[i]; i++) {
+                        if (line[i] == '*') {
+                                memcpy(backup[0], prev, N);
+                                memcpy(backup[1], line, N);
+                                memcpy(backup[2], next, N);
+                                j = 0;
+                                push(&j, g, &prev[i-1]);
+                                push(&j, g, &prev[i]);
+                                push(&j, g, &prev[i+1]);
+                                push(&j, g, &line[i-1]);
+                                push(&j, g, &line[i+1]);
+                                push(&j, g, &next[i-1]);
+                                push(&j, g, &next[i]);
+                                push(&j, g, &next[i+1]);
+                                if (j == 2) sum += g[0] * g[1];
+                                memcpy(prev, backup[0], N);
+                                memcpy(line, backup[1], N);
+                                memcpy(next, backup[2], N);
+                        }
+                }
+                memcpy(prev, line, N);
+        }
+
+        printf("%d\n", sum);
+        return 0;
+}