init

1 files changed, 149 insertions, 0 deletions

diff --git a/advent-of-code/2023/03/part2.c b/advent-of-code/2023/03/part2.c
new file mode 100644
index 0000000..a5ab825
--- /dev/null
+++ b/advent-of-code/2023/03/part2.c
@@ -0,0 +1,149 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <ctype.h>
+#include <assert.h>
+
+#include "vec.h"
+#include "str.h"
+#include "map.h"
+
+void* read_input() {
+    FILE* fp = fopen("./input", "r");
+    void *vec = new_vec();
+    while(1) {
+        char *line = fgetline(fp);
+        if (line == NULL) break;
+        char *stripped = str_strip(line);
+        if (strlen(stripped) == 0) break;
+        vec_push_back(vec, stripped);
+    }
+    return vec;
+}
+
+typedef struct {
+    int line;
+    int column;
+    int value;
+    int length;
+} num_t;
+
+char *compose_key(int x, int y) {
+    void* ss = new_ss();
+    ss_add(ss, "%d,%d", x, y);
+    return ss_cstr(ss);
+}
+
+void *parse_nums(void *schema) {
+    void *nums = new_vec();
+    int j = 0;
+    const int IN_NUM = 0, IDLE = 1;
+    int state = IDLE;
+    for (int i = 0; i < vec_size(schema); i++) {
+        char *line = vec_get(schema, i);
+        int line_len = strlen(line);
+        int value = 0;
+        int length = 0;
+        state = IDLE;
+        j = 0;
+        while (1) {
+            char c = '.';
+            if (j < line_len) c = line[j];
+            if (state == IDLE) {
+                if (isdigit(c)) {
+                    state = IN_NUM;
+                    continue;
+                } else {
+                    j++;
+                    if (j >= line_len) break;
+                    continue;
+                }
+            } else if (state == IN_NUM) {
+                if (isdigit(c)) {
+                    value = value * 10 + (c - '0'); 
+                    length++;
+                    j++;
+                    continue;
+                } else {
+                    num_t *n = malloc(sizeof(num_t));
+                    *n = (num_t){
+                        .line = i,
+                        .column = j - length,
+                        .value = value,
+                        .length = length
+                    };
+                    vec_push_back(nums, n);
+                    value = 0;
+                    length = 0;
+                    state = IDLE;
+                    if (j >= line_len) break;
+                    continue;
+                }
+            }
+        }
+    }
+    return nums;
+}
+
+char char_at(void *schema, int line, int column) {
+    char *buf = vec_get(schema, line);
+    return buf[column];
+}
+
+void mark_asterisks(void *asterisks, num_t *num, int x, int y) {
+    const char *key = compose_key(x, y);
+    void *num_list = dict_get(asterisks, key);
+    if (num_list == NULL) {
+        num_list = new_vec();
+        dict_set(asterisks, key, num_list);
+    }
+    vec_push_back(num_list, num);
+}
+
+void find_asterisks(void *schema, void *asterisks, num_t *num) {    
+    int line_len = vec_size(schema);
+    int col_len = strlen(vec_get(schema, 0));
+    for (int i = num->column - 1; i < num->column + num->length + 1; i++) {
+        if (num->line - 1 < 0) continue;
+        if (i < 0 || i >= col_len) continue;
+        char c = char_at(schema, num->line - 1, i);
+        if (c == '*') mark_asterisks(asterisks, num, num->line - 1, i);
+    }
+    for (int i = num->column - 1; i < num->column + num->length + 1; i++) {
+        if (num->line + 1 >= line_len) continue;
+        if (i < 0 || i >= col_len) continue;
+        char c = char_at(schema, num->line + 1, i);
+        if (c == '*') mark_asterisks(asterisks, num, num->line + 1, i);
+    }
+    if (num->column - 1 >= 0) {
+        char c = char_at(schema, num->line, num->column - 1);
+        if (c == '*') mark_asterisks(asterisks, num, num->line, num->column - 1);
+    }
+    if (num->column + num->length < col_len) {
+        char c = char_at(schema, num->line, num->column + num->length);
+        if (c == '*') mark_asterisks(asterisks, num, num->line, num->column + num->length);
+    }
+}
+
+int main() {
+    void *schema = read_input();
+    void *nums = parse_nums(schema);
+    int sum = 0;
+    void *asterisks = new_dict();
+    for (int i = 0; i < vec_size(nums); i++) {
+        num_t *num = vec_get(nums, i);
+        find_asterisks(schema, asterisks, num);
+    }
+    for (void *iter = dict_begin(asterisks);
+            iter != NULL;
+            iter = dict_next(asterisks, iter)) {
+        void *list = dict_iter_value(iter);
+        if (vec_size(list) == 2) {
+            num_t* n1 = vec_get(list, 0);
+            num_t* n2 = vec_get(list, 1);
+            sum += n1->value * n2->value;
+        }
+    }
+    printf("%d\n", sum);
+    return 0;
+}