From cb0b1542582f03af967635ee0cd266f015ae44f2 Mon Sep 17 00:00:00 2001
From: Mistivia <i@mistivia.com>
Date: Mon, 22 Dec 2025 04:09:54 +0800
Subject: day 6 part 2

---
 06/part2.c | 114 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 114 insertions(+)
 create mode 100644 06/part2.c

diff --git a/06/part2.c b/06/part2.c
new file mode 100644
index 0000000..38c8ecc
--- /dev/null
+++ b/06/part2.c
@@ -0,0 +1,114 @@
+#include <algds/str.h>
+#include <algds/vec.h>
+#include <ctype.h>
+#include <string.h>
+
+#define PANIC do { \
+    fprintf(stderr, "panic at %s:%d\n", __FILE__, __LINE__); \
+    abort(); \
+} while (0)
+
+StringVector read_mat() {
+    StringVector mat;
+    StringVector_init(&mat);
+    while (1) {
+        char *l = fgetline(stdin);
+        if (!l) {
+            return mat;
+        }
+        if (strlen(l) == 0) {
+            return mat;
+        }
+        int len = strlen(l);
+        if (l[len - 1] == '\n') {
+            l[len - 1] = '\0';
+        }
+        StringVector_push_back(&mat, l);
+    }
+    return mat;
+}
+
+char mat_read(StringVector *mat, int x, int y) {
+    const char *line = *StringVector_ref(mat, y);
+    return line[x];
+}
+
+char scan_column(StringVector *mat, int x, int *n) {
+    int out = 0;
+    int have_digit = 0;
+    for (int y = 0; y < mat->size - 1; y++) {
+        char c = mat_read(mat, x, y);
+        if (c == ' ') {
+            continue;
+        } else if (isdigit(c)) {
+            out = out * 10 + c - '0';
+            have_digit = 1;
+        } else {
+            PANIC;
+        }
+    }
+    if (have_digit) {
+        *n = out;
+    }
+    return mat_read(mat, x, mat->size - 1);
+}
+
+int main() {
+    StringVector lines = read_mat();
+    long maxlen = 0;
+    for (int i = 0; i < lines.size; i++) {
+        long len = strlen(lines.buffer[i]);
+        if (len > maxlen) {
+            maxlen = len;
+        }
+    }
+    for (int i = 0; i < lines.size; i++) {
+        long len = strlen(lines.buffer[i]);
+        if (len < maxlen) {
+            char *spaces = malloc(maxlen - len + 1);
+            memset(spaces, '0', maxlen - len);
+            spaces[maxlen - len] = '\0';
+            char *ns = malloc(maxlen + 1);
+            strcat(ns, lines.buffer[i]);
+            strcat(ns + len, spaces);
+            free(spaces);
+            free((void*)lines.buffer[i]);
+            lines.buffer[i] = ns;
+        }
+    }
+    long ret = 0;
+    IntVector read_nums;
+    IntVector_init(&read_nums);
+    for (int x = strlen(lines.buffer[0]) - 1; x >= 0; x--) {
+        int cur = -1;
+        char sym = scan_column(&lines, x, &cur);
+        if (cur >= 0) {
+            IntVector_push_back(&read_nums, cur);
+        }
+        if (sym == '+') {
+            long sum = 0;
+            for (int i = 0; i < read_nums.size; i++) {
+                sum += read_nums.buffer[i];
+            }
+            ret += sum;
+            IntVector_free(&read_nums);
+            IntVector_init(&read_nums);
+        } else if (sym == '*') {
+            long prod = 1;
+            for (int i = 0; i < read_nums.size; i++) {
+                prod *= read_nums.buffer[i];
+            }
+            ret += prod;
+            IntVector_free(&read_nums);
+            IntVector_init(&read_nums);
+        }
+    }
+    printf("%ld\n", ret);
+    
+    IntVector_free(&read_nums);
+    for (int i = 0; i < lines.size; i++) {
+        free((void*)lines.buffer[i]);
+    }
+    StringVector_free(&lines);
+    return 0;
+}
\ No newline at end of file
-- 
cgit v1.0