schrockwell
/aoc2024
/amendments
/1
Day 1 solution and example input
schrockwell made amendment 1 10 months ago
--- 01-example.txt Mon Dec 1 14:32:38 1924
+++ 01-example.txt Mon Dec 1 14:32:38 1924
@@ -0,0 +1 @@
+3 4
4 3
2 5
1 3
3 9
3 3
--- day1.c Mon Dec 8 18:57:33 1924
+++ day1.c Mon Dec 8 18:57:33 1924
@@ -0,0 +1,134 @@
+#include <console.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+// CONSTANTS
+
+#define MAX_LINE_LENGTH 32
+#define MAX_LIST_SIZE 1024
+
+// TYPES
+
+typedef struct {
+ long int key;
+ int value;
+} kv;
+
+// GLOBALS
+
+long int firstList[MAX_LIST_SIZE];
+long int secondList[MAX_LIST_SIZE];
+
+kv secondHist[MAX_LIST_SIZE];
+
+// FUNCTIONS
+
+int compare_longs(const void *a, const void *b) {
+ long int int_a = *(const long int *)a;
+ long int int_b = *(const long int *)b;
+
+ if (int_a < int_b) return -1;
+ if (int_a > int_b) return 1;
+ return 0;
+}
+
+int build_histogram(kv hist[], long int arr[], int count) {
+ int i = 0;
+ int keyCount = 0;
+
+ for (i = 0; i < count; i++) {
+ long int key = arr[i];
+ int histIndex = findHistIndex(hist, keyCount, key);
+
+ if (histIndex == -1) {
+ histIndex = keyCount;
+ keyCount++;
+ }
+
+ hist[histIndex].key = key;
+ hist[histIndex].value++;
+ }
+
+ return keyCount;
+}
+
+int findHistIndex(kv hist[], int count, long int key) {
+ int i = 0;
+
+ for (i = 0; i < count; i++) {
+ if (hist[i].key == key) {
+ return i;
+ }
+ }
+
+ return -1;
+}
+
+void main(int argc, char* argv) {
+ //char *filename = "01-input.txt";
+ char *filename = "01-example.txt";
+
+ int index = 0;
+ long int firstAnswer = 0;
+ long int secondAnswer = 0;
+ int i = 0;
+ int histCount, histIndex;
+
+ FILE *file;
+ char line[MAX_LINE_LENGTH];
+
+ file = fopen(filename, "r");
+ if (file == NULL) {
+ perror("Error opening file");
+ return;
+ }
+
+ printf("Reading %s... ", filename);
+
+ while (fgets(line, sizeof(line), file) != NULL) {
+ long int num1, num2;
+ if (sscanf(line, "%ld %ld", &num1, &num2) != 2) {
+ printf("error parsing line %d", index);
+ return;
+ }
+
+ firstList[index] = num1;
+ secondList[index] = num2;
+ index++;
+ }
+
+ fclose(file);
+
+ printf("read %d lines\n", index);
+
+ // PART 1
+
+ printf("Sorting first list...\n");
+ qsort(firstList, index, sizeof(long int), compare_longs);
+
+ printf("Sorting second list...\n");
+ qsort(secondList, index, sizeof(long int), compare_longs);
+
+ for (i = 0; i < index; i++) {
+ firstAnswer = firstAnswer + abs(firstList[i] - secondList[i]);
+ }
+
+ // PART 2
+
+ printf("Calculating histogram...\n");
+ histCount = build_histogram(secondHist, secondList, index);
+
+ //for (i = 0; i < histCount; i++) {
+ // printf("%ld => %d\n", secondHist[i].key, secondHist[i].value);
+ //}
+
+ for (i = 0; i < index; i++) {
+ histIndex = findHistIndex(secondHist, histCount, firstList[i]);
+ if (histIndex == -1) continue;
+
+ secondAnswer += firstList[i] * secondHist[histIndex].value;
+ }
+
+ printf("Part 1: %ld\n", firstAnswer);
+ printf("Part 2: %ld\n", secondAnswer);
+}