feat: add day 3

day_3.c

@@ -0,0 +1,146 @@
+//
+// Created by lennart on 12/6/23.
+//
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <stdbool.h>
+#include <ctype.h>
+#include "input_handler.h"
+
+typedef struct {
+    char **data;
+    int height;
+    int width;
+} PartsMap;
+
+// Functions
+PartsMap* load_map(const char *file_name);
+void free_map(PartsMap *map);
+bool is_adjacent_to_symbol(PartsMap *map, int row, int col, int len);
+bool is_gear(PartsMap *map, int g_row, int g_col, int *num1, int *num2);
+
+int main() {
+    PartsMap *map = load_map("day_3.txt");
+
+    // Part 1 - Iterate over each row and find numbers with adjacent symbols
+    int sum = 0;
+    for(int row = 0; row < map->height; row++) {
+        const char *begin = &map->data[row][0];
+        char *pos = (char*) begin;
+        while(*pos != 0) {
+            const char *before = pos;
+            if(isdigit(*pos)) {
+                unsigned long num = strtoul(before, &pos, 10);
+                if(is_adjacent_to_symbol(map, row, (int) (before - begin), (int) (pos - before))) {
+                    sum += (int) num;
+                }
+            } else {
+                pos++;
+            }
+        }
+    }
+    printf("Result #1: %i\n", sum);
+
+    // Part 2 - Iterate over each row and find gear symbols (*) with 2 adjacent numbers
+    sum = 0;
+    for(int row = 0; row < map->height; row++) {
+        for(int col = 0; col < map->width; col++) {
+            if(map->data[row][col] == '*') {
+                int num1, num2;
+                if(is_gear(map, row, col, &num1, &num2)) {
+                    sum += num1 * num2;
+                }
+            }
+        }
+    }
+    printf("Result #2: %i", sum);
+
+    free_map(map);
+}
+
+bool is_gear(PartsMap *map, int g_row, int g_col, int *num1, int *num2) {
+    int count = 0;
+
+    int rowMin = max(g_row - 1, 0);
+    int rowMax = min(g_row + 1, map->height - 1);
+    int colMin = max(g_col - 1, 0);
+    int colMax = min(g_col + 1, map->width - 1);
+
+    for(int row = rowMin; row <= rowMax; row++) {
+        const char *begin = &map->data[row][0];
+        char *pos = &map->data[row][colMin];
+        while(isdigit(*pos) && pos > begin) {
+            pos--;
+        }
+        while(pos - begin <= colMax) {
+            if(isdigit(*pos)) {
+                const char *before = pos;
+                unsigned long num = strtoul(before, &pos, 10);
+                if(++count == 1) {
+                    *num1 = (int) num;
+                } else if(count == 2) {
+                    *num2 = (int) num;
+                } else {
+                    return false; // More than 2 adjacent numbers
+                }
+            } else {
+                pos++;
+            }
+        }
+    }
+    return count == 2;
+}
+
+bool is_adjacent_to_symbol(PartsMap *map, int row, int col, int len) {
+    int rowMin = max(row - 1, 0);
+    int rowMax = min(row + 2, map->height);
+    int colMin = max(col - 1, 0);
+    int colMax = min(col + len + 1, map->width);
+    for(int cr = rowMin; cr < rowMax; cr++) {
+        for(int cc = colMin; cc < colMax; cc++) {
+            char c = map->data[cr][cc];
+            if(c != '.' && !isdigit(c)) {
+                return true;
+            }
+        }
+    }
+    return false;
+}
+
+PartsMap* load_map(const char *file_name) {
+    FILE *f = fopen(file_name, "r");
+    if(f == NULL) {
+        printf("ERROR: Input file not found!");
+        exit(1);
+    }
+
+    char *buffer = NULL;
+    int bufferLen = 0;
+
+    size_t length = 16;
+    PartsMap *map = malloc(sizeof (PartsMap));
+    map->height = 0;
+    map->data = malloc(sizeof (map->data) * length);
+    while(!feof(f)) {
+        if(map->height >= length) {
+            map->data = realloc(map->data, sizeof (map->data) * (length *= 2));
+        }
+        read_line(f, &buffer, &bufferLen);
+        map->data[map->height++] = strdup(buffer);
+    }
+    map->width = strlen(map->data[0]);
+
+    fclose(f);
+    free(buffer);
+    return map;
+}
+
+void free_map(PartsMap *map) {
+    for(size_t row = 0; row < map->height; row++) {
+        free(map->data[row]);
+    }
+    free(map->data);
+    free(map);
+}