1 files changed, 144 insertions, 0 deletions
diff --git a/Advent-of-Code-2021/AOC-20/main.c b/Advent-of-Code-2021/AOC-20/main.c
new file mode 100644
index 0000000..1dbcdc9
--- /dev/null
+++ b/Advent-of-Code-2021/AOC-20/main.c
@@ -0,0 +1,144 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <assert.h>
+#include <string.h>
+
+#if 0
+#define PART_1
+#else
+#define PART_2
+#endif
+
+#if 0
+    #define FILE_PATH "example.txt"
+    #define T_WIDTH  5
+    #define T_HEIGHT 5
+#else
+    #define FILE_PATH "input.txt"
+    #define T_WIDTH  100
+    #define T_HEIGHT 100
+#endif
+
+#define WIDTH  256
+#define HEIGHT 256
+
+#define OFFSET_X ((WIDTH/2)  - (T_WIDTH/2))
+#define OFFSET_Y ((HEIGHT/2) - (T_HEIGHT/2))
+
+
+int board[WIDTH][HEIGHT];
+int new_board[WIDTH][HEIGHT];
+int enchance_alg[512];
+
+void parse()
+{
+    FILE *fp = fopen(FILE_PATH, "r");
+    if(!fp) {
+        fprintf(stderr, "ERROR: Could not open file: %s\n", FILE_PATH);
+        exit(EXIT_FAILURE);
+    }
+
+    char line[1024] = {0};
+
+    fgets(line, sizeof(line), fp);
+    for(int i = 0; i < 512; i++)
+        if(line[i] == '.')
+            enchance_alg[i] = 0;
+        else
+            enchance_alg[i] = 1;
+
+    fgets(line, sizeof(line), fp);
+
+    char ch;
+    int i = 0;
+    while((ch = getc(fp)) != EOF)
+    {
+        if(ch == '\n') continue;
+        else if(ch == '.')
+            board[i%T_WIDTH + OFFSET_X][i/T_WIDTH + OFFSET_Y] = 0;
+        else if(ch == '#')
+            board[i%T_WIDTH + OFFSET_X][i/T_WIDTH + OFFSET_Y] = 1;
+
+        i++;
+    }
+
+
+    fclose(fp);
+}
+
+int generate_index(int *vals)
+{
+    int index = 0;
+    for(int i = 0; i < 9; i++)
+    {
+        index |= (vals[8-i] & 1)<< i;
+    }
+    return index;
+}
+
+void enchance()
+{
+    for(int i = 0; i < HEIGHT; i++)
+    {
+        for(int j = 0; j < WIDTH; j++)
+        {
+            int vals[9];
+            for(int y = -1; y <= 1; y++)
+                for(int x = -1; x <= 1; x++)
+                {
+                    int vals_i = (y+1) * 3 + (x+1);
+                    if(i+y < 0 || i+y >= HEIGHT ||
+                       j+x < 0 || j+x >= WIDTH)
+                        vals[vals_i] = board[j][i];
+                    else
+                        vals[vals_i] = board[j+x][i+y];
+                }
+            new_board[j][i] = enchance_alg[generate_index(vals)];
+        }
+    }
+    memcpy(board, new_board, sizeof(board));
+}
+
+void print_board()
+{
+    for(int i = 0; i < HEIGHT; i++)
+    {
+        for(int j = 0; j < WIDTH; j++)
+            if(board[j][i] == 0) putc('.', stdout);
+            else                 putc('#', stdout);
+
+        putc('\n', stdout);
+    }
+}
+
+void print_alg()
+{
+    for(int i = 0; i < 512; i++)
+    {
+        if(enchance_alg[i] == 0) putc('.', stdout);
+        else                     putc('#', stdout);
+    }
+    putc('\n', stdout);
+}
+
+
+int main(void)
+{
+    parse();
+
+#ifdef PART_1
+    for(int i = 0; i < 2; i++)
+#endif
+#ifdef PART_2
+    for(int i = 0; i < 50; i++)
+#endif
+        enchance();
+
+    int lit = 0;
+    for(int i = 0; i < HEIGHT; i++)
+        for(int j = 0; j < WIDTH; j++)
+            if(board[j][i] == 1) lit++;
+
+    printf("%d pixels are lit\n", lit);
+    return 0;
+}