finish day 4

day4.jai

@@ -17,6 +17,7 @@ main :: () {
     content := read_entire_file("day4.input");
 
     solve_first(content);
+    solve_second(content);
 }
 
 solve_first :: (input: string) {
@@ -54,6 +55,67 @@ solve_first :: (input: string) {
     print("%\n", removable);
 }
 
+Point :: struct {
+    line_index: int;
+    char_index: int;
+}
+
+solve_second :: (input: string) {
+    all_lines := split(input, #char "\n");
+    lines: [..][..]u8;
+    array_reserve(*lines, all_lines.count);
+    for line: all_lines {
+        if line.count == 0 continue;
+        chars: [..]u8;
+        array_reserve(*chars, line.count);
+        for line {
+            array_add(*chars, it);
+        }
+        array_add(*lines, chars);
+    }
+    assert(lines[0].count != 0);
+    line_length := lines[0].count;
+    removed := 0;
+    any_removed := true;
+    while any_removed {
+        any_removed = false;
+        points_to_remove: [..]Point;
+        points_to_remove.allocator = temp;
+        array_reserve(*points_to_remove, line_length);
+	defer reset_temporary_storage();
+	for line, line_index: lines {
+	    if line.count == 0 continue;
+	    for char, char_index: line {
+		if char == #char "." continue;
+		surrounding_chars: [8]u8;
+                surrounding_chars_index := 0;
+                for dy: -1..1 {
+                    for dx: -1..1 {
+                        if dx == 0 && dy == 0 continue;
+                        defer surrounding_chars_index += 1;
+                        x := char_index + dx;
+                        if x < 0 || line.count <= x continue;
+                        y := line_index + dy;
+                        if y < 0 || lines.count <= y continue;
+                        surrounding_chars[surrounding_chars_index] = lines[y][x];
+                    }
+                }
+                if array_count(surrounding_chars, (char: u8) -> bool { return char == #char "@"; }) < 4 {
+                    removed += 1;
+                    any_removed = true;
+                    array_add(*points_to_remove, .{line_index=line_index, char_index=char_index});
+                }
+            }
+        }
+
+        for points_to_remove {
+            lines[it.line_index][it.char_index] = #char ".";
+        }
+    }
+    print("%\n", removed);
+}
+
+
 array_count :: (arr: []$T, f: (t: T) -> bool) -> int {
     total := 0;
     for arr {