1 files changed, 144 insertions, 0 deletions
diff --git a/Advent-of-Code-2023/aoc-3/main.c b/Advent-of-Code-2023/aoc-3/main.c
new file mode 100644
index 0000000..2041f4d
--- /dev/null
+++ b/Advent-of-Code-2023/aoc-3/main.c
@@ -0,0 +1,144 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <ctype.h>
+#include <stdint.h>
+
+// too low 425996
+
+// #define FILENAME "sample.txt"
+#define FILENAME "input.txt"
+
+#define BOARD_MAX 256
+#define NUMBERS_MAX 2048
+
+#define MIN(a,b) (((int)(a)<(int)(b))?(a):(b))
+#define MAX(a,b) (((int)(a)>(int)(b))?(a):(b))
+
+typedef struct {
+    int number;
+    
+    size_t x;
+    size_t y;
+    size_t len;
+} num;
+
+typedef struct {
+    size_t x;
+    size_t y;
+
+    uint64_t p;
+    size_t nrefs;
+} gear;
+
+void num_print(num number);
+int num_near_symbol(num number);
+
+void gear_print(gear g);
+void gear_add(size_t x, size_t y, size_t number);
+
+static num numbers[NUMBERS_MAX];
+static size_t nnumbers;
+
+static gear gears[NUMBERS_MAX];
+static size_t ngears;
+
+static char board[BOARD_MAX][BOARD_MAX];
+static size_t width;
+static size_t height;
+
+int main(void)
+{
+    FILE *fp = fopen(FILENAME, "r");
+    if(!fp) {
+        perror("fopen: failed");
+        return 1;
+    }
+
+    char line[256];
+    
+    fgets(line, sizeof(line), fp);
+    width = strlen(line) - 1; // minus \n
+
+    fseek(fp, 0, SEEK_SET);
+
+    // load the numbers
+    while(fgets(line, sizeof(line), fp)) {
+        // copy the board
+        memcpy(board[height], line, width);
+
+        char numstr[16] = {0};
+        size_t len = 0;
+        for(size_t i = 0; i < width; i++) {          
+            while(isdigit(board[height][i])){
+                numstr[len] = board[height][i];
+                i++; len++;
+            }
+            
+            if(numstr[0] != 0) {
+                numbers[nnumbers++] = (num){ atoi(numstr), i-len, height, len };
+                memset(numstr, 0, sizeof(numstr));
+                len = 0;
+            }
+        }
+        
+        height++;
+    }
+    
+    fclose(fp);
+    
+    uint64_t sum = 0;
+    for(size_t i = 0; i < nnumbers; i++) {
+        if(num_near_symbol(numbers[i])) {
+            sum += numbers[i].number;
+        }
+    }
+
+    printf("Part 1: %lu\n", sum);
+
+    sum = 0;
+    for(size_t i = 0; i < ngears; i++) {
+        if(gears[i].nrefs == 2) sum += gears[i].p;
+    }
+
+    printf("Part 2: %lu\n", sum);
+    return 0;
+}
+
+int num_near_symbol(num number)
+{
+    for(size_t i = MAX(number.y - 1, 0); i <= MIN(number.y + 1, height-1); i++)
+        for(size_t j = MAX(number.x - 1, 0); j <= MIN(number.x + number.len, width-1); j++) {
+            if((i == number.y) && ((j >= number.x) && (j < number.x + number.len))) continue;
+               
+            if(board[i][j] == '*') gear_add(j, i, number.number);
+            if(board[i][j] != '.') return 1;
+        }
+    return 0;
+}
+
+void num_print(num number)
+{
+    printf("%d: %ld %ld %ld\n", number.number, number.len, number.x, number.y);
+}
+
+void gear_print(gear g)
+{
+    printf("%ld %ld %ld %ld\n", g.x, g.y, g.nrefs, g.p);
+}
+
+void gear_add(size_t x, size_t y, size_t number)
+{
+    for(size_t i = ngears - 1; i < ngears; i--)
+        if((gears[i].x == x) && (gears[i].y == y)) {
+            gears[i].nrefs++;
+            gears[i].p *= number;
+            return;
+        }
+
+    gears[ngears].x = x;
+    gears[ngears].y = y;
+    gears[ngears].p = number;
+    gears[ngears].nrefs = 1;
+    ngears++;
+}