day 11

[advent21.git] / 11a.c

diff --git a/11a.c b/11a.c
new file mode 100644 (file)
index 0000000..0ed0f8d
--- /dev/null
+++ b/11a.c
@@ -0,0 +1,46 @@
+#include <stdio.h>
+
+void flash(char grid[10][10], int *flashes, int x, int y)
+{
+       //already flashed or not charged up enough
+       if (grid[y][x] == 0 || grid[y][x] < 10)
+               return;
+       (*flashes)++;
+       grid[y][x] = 0;
+       for (int dy = -1; dy<=1; dy++)
+               for (int dx = -1; dx<=1; dx++)
+                       if ( (dx != 0 || dy != 0) &&
+                                       x+dx >= 0 && x+dx < 10 &&
+                                       y+dy >= 0 && y+dy < 10) {
+                               if (grid[y+dy][x+dx] != 0)
+                                       grid[y+dy][x+dx]++;
+                               flash(grid, flashes, x+dx, y+dy);
+                       }
+}
+
+int main()
+{
+       int x = 0, y = 0;
+       int c;
+       char grid[10][10];
+       while( (c = getchar()) != EOF) {
+               if (c == '\n') {
+                       y++;
+                       x = 0;
+               } else {
+                       grid[y][x++] = c-'0';
+               }
+       }
+
+       int flashes = 0;
+       for (int i = 0; i<100; i++) {
+               for (int y = 0; y<10; y++)
+                       for (int x = 0; x<10; x++)
+                               grid[y][x]++;
+               for (int y = 0; y<10; y++)
+                       for (int x = 0; x<10; x++)
+                               flash(grid, &flashes, x, y);
+       }
+       
+       printf("%d\n", flashes);
+}