Day15 C

day15/c/day15.c

@@ -0,0 +1,112 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#define LINE_MAX_LENGTH 32*1024
+#define STRBUF_SIZE 64
+#define NUM_BOXES 256
+#define MAX_LENS_PER_BOX 32
+#define NUM_0_CHARCODE 48
+
+typedef struct lens {
+    char label[STRBUF_SIZE];
+    int label_len;
+    int focal_length;
+} lens_t;
+
+typedef struct box {
+    lens_t lenses[MAX_LENS_PER_BOX];
+    int lenses_num;
+} box_t;
+
+int hash(char*, int);
+
+int main() {
+    char *p, *buf, c, *start;
+
+    buf = (char *)malloc(LINE_MAX_LENGTH);
+    memset(buf, 0, LINE_MAX_LENGTH);
+    p = buf;
+    char strbuf[STRBUF_SIZE];
+    memset(strbuf, 0, STRBUF_SIZE * sizeof(char));
+
+    box_t boxes[NUM_BOXES];
+    memset(boxes, 0, NUM_BOXES * sizeof(box_t));
+
+    int sum = 0;
+    while ((c = getchar()) != EOF) {
+        *p++ = c;
+        if (c == '\n') {
+            p = buf;
+            start = p;
+            while (*p != '\0') {
+                while (*p != ',' && *p != '\n') p++;
+                strncpy(strbuf, start, p - start);
+                sum += hash(strbuf, p - start);
+                // Find = or -
+                while (*p != '-' && *p != '=') p--;
+                int box_num = hash(strbuf, p - start);
+                if (*p == '-') {
+                    for (int i = 0; i < boxes[box_num].lenses_num; i++) {
+                        if (boxes[box_num].lenses[i].label_len == p - start && !strncmp(boxes[box_num].lenses[i].label, strbuf, p - start)) {
+                            for (int j = i; j < boxes[box_num].lenses_num - 1; j++) {
+                                memcpy(&boxes[box_num].lenses[j], &boxes[box_num].lenses[j + 1], sizeof(lens_t));
+                            }
+                            boxes[box_num].lenses_num--;
+                            break;
+                        }
+                    }
+                    p++;
+                } else if (*p == '=') {
+                    int found = 0;
+                    int focal_length = *(p+1) - NUM_0_CHARCODE;
+                    for (int i = 0; i < boxes[box_num].lenses_num; i++) {
+                        if (boxes[box_num].lenses[i].label_len == p - start && !strncmp(boxes[box_num].lenses[i].label, strbuf, p - start)) {
+                            boxes[box_num].lenses[i].focal_length = focal_length;
+                            found = 1;
+                            break;
+                        }
+                    }
+
+                    if (!found) {
+                        boxes[box_num].lenses[boxes[box_num].lenses_num].label_len = p - start;
+                        boxes[box_num].lenses[boxes[box_num].lenses_num].focal_length = focal_length;
+                        strncpy(boxes[box_num].lenses[boxes[box_num].lenses_num].label, strbuf, p - start);
+                        boxes[box_num].lenses_num++;
+                    }
+                    p++;
+                    p++;
+                }
+
+                p++;
+                start = p;
+                memset(strbuf, 0, STRBUF_SIZE * sizeof(char));
+            }
+            memset(buf, 0, LINE_MAX_LENGTH);
+            p = buf;
+        }
+    }
+
+    int part2 = 0;
+    for (int i = 0; i < NUM_BOXES; i++) {
+        for (int j = 0; j < boxes[i].lenses_num; j++) {
+            part2 += (i+1) * (j+1) * boxes[i].lenses[j].focal_length;
+        }
+    }
+
+    printf("%i\n", sum);
+    printf("%i\n", part2);
+    free(buf);
+}
+
+int hash(char *str, int len) {
+    int current_value = 0;
+
+    for (int i = 0; i < len; i++) {
+        current_value += str[i];
+        current_value *= 17;
+        current_value %= 256;
+    }
+
+    return current_value;
+}

day15/sample.txt

@@ -0,0 +1 @@
+rn=1,cm-,qp=3,cm=2,qp-,pc=4,ot=9,ab=5,pc-,pc=6,ot=7