day 4 part 2

1 files changed, 119 insertions, 0 deletions

diff --git a/04/part2.c b/04/part2.c
index e69de29..e715fdb 100644
--- a/04/part2.c
+++ b/04/part2.c
@@ -0,0 +1,119 @@
+#include <algds/str.h>
+#include <algds/vec.h>
+
+StringVector readmap() {
+    StringVector map;
+    StringVector_init(&map);
+    while (1) {
+        char *l = fgetline(stdin);
+        if (!l) {
+            return map;
+        }
+        char *nl = str_strip(l);
+        free(l);
+        l = nl;
+        if (strlen(l) == 0) {
+            return map;
+        }
+        StringVector_push_back(&map, l);
+    }
+    return map;
+}
+
+char map_read(StringVector *map, int x, int y) {
+    int height = StringVector_len(map);
+    if (height == 0) {
+        return '\0';
+    }
+    int width = strlen(*StringVector_ref(map, 0));
+    if (x >= width || x < 0) {
+        return '\0';
+    }
+    if (y >= height || y < 0) {
+        return '\0';
+    }
+    return (*StringVector_ref(map, y))[x];
+}
+
+void map_set(StringVector *map, int x, int y, char c) {
+    int height = StringVector_len(map);
+    if (height == 0) {
+        return;
+    }
+    int width = strlen(*StringVector_ref(map, 0));
+    if (x >= width || x < 0) {
+        return;
+    }
+    if (y >= height || y < 0) {
+        return;
+    }
+    ((char*)*StringVector_ref(map, y))[x] = c;
+}
+
+
+bool is_paper(StringVector *map, int x, int y) {
+    char c = map_read(map, x, y);
+    return c == '@';
+}
+
+int count_adjacent(StringVector *map, int x, int y) {
+    int count = 0;
+    if (is_paper(map, x - 1, y - 1)) {
+        count++;
+    }
+    if (is_paper(map, x - 1, y)) {
+        count++;
+    }
+    if (is_paper(map, x, y - 1)) {
+        count++;
+    }
+    if (is_paper(map, x + 1, y + 1)) {
+        count++;
+    }
+    if (is_paper(map, x + 1, y)) {
+        count++;
+    }
+    if (is_paper(map, x, y + 1)) {
+        count++;
+    }
+    if (is_paper(map, x + 1, y - 1)) {
+        count++;
+    }
+    if (is_paper(map, x - 1, y + 1)) {
+        count++;
+    }
+    return count;
+}
+
+int iter(StringVector *map, int height, int width) {
+    int forked = 0;
+    for (int x = 0; x < width; x++) {
+        for (int y = 0; y < height; y++) {
+            if (map_read(map, x, y) != '@') {
+                continue;
+            }
+            if (count_adjacent(map, x, y) < 4) {
+                map_set(map, x, y, 'x');
+                forked++;
+            }
+        }
+    }
+    return forked;
+}
+
+int main() {
+    StringVector map = readmap();
+    int height = StringVector_len(&map);
+    int width = strlen(*StringVector_ref(&map, 0));
+    int res = 0;
+    while (1) {
+        int n = iter(&map, height, width);
+        if (n > 0) {
+            res += n;
+        } else {
+            break;
+        }
+    }
+    printf("%d\n", res);
+    return 0;
+}
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