Initial commit

2020/day06/day06.c

@@ -0,0 +1,58 @@
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+int main(int argc, char *argv[]) {
+  if (argc < 2) {
+    printf("Usage: %s <input file>\n", argv[0]);
+    return 0;
+  }
+
+  FILE *fp = fopen(argv[1], "r");
+  if (fp == NULL) {
+    printf("Could not open file %s\n", argv[1]);
+    return 1;
+  }
+
+  bool flag_newline = false;
+  unsigned int answer_count = 0;
+  unsigned int counts[26] = {0};
+  unsigned int part1 = 0;
+  unsigned int part2 = 0;
+  for (char c = getc(fp); c != EOF; c = getc(fp)) {
+    if (c == '\n' && flag_newline) {
+      for (int i = 0; i < 26; ++i) {
+        if (counts[i] > 0) {
+          part1++;
+        }
+        if (counts[i] == answer_count) {
+          part2++;
+        }
+        counts[i] = 0;
+      }
+      flag_newline = false;
+      answer_count = 0;
+    } else if (c == '\n') {
+      flag_newline = true;
+      answer_count++;
+    } else {
+      counts[c - 'a']++;
+      flag_newline = false;
+    }
+  }
+
+  for (int i = 0; i < 26; ++i) {
+    if (counts[i] > 0) {
+      part1++;
+    }
+    if (counts[i] == answer_count) {
+      part2++;
+    }
+  }
+
+  printf("%u\n", part1);
+  printf("%u\n", part2);
+
+  fclose(fp);
+  return 0;
+}

2020/day06/day06.dyalog

@@ -0,0 +1,4 @@
+ p←⊃⎕NGET'input'1
+ p←(~p∊⊂'')⊆p
+ +/{≢⊃∪/⍵}¨p  ⍝ Part 1
+ +/{≢⊃∩/⍵}¨p  ⍝ Part 2

2020/day06/day06.rkt

@@ -0,0 +1,37 @@
+#lang racket
+
+(module+ test
+  (require rackunit))
+
+(module+ main
+  (displayln "Day 6"))
+
+(define (read-input filename)
+  (string-split (file->string filename) "\n\n"))
+
+(define (count-unique str)
+  (set-count (set-remove (list->set (string->list str)) #\newline)))
+
+(define (part1 filename)
+  (apply + (map count-unique (read-input filename))))
+
+(module+ test
+  (check-equal? (part1 "test") 11))
+
+(module+ main
+  (displayln (part1 "input")))
+
+(define (count-intersection str)
+  (define answers (string-split str "\n"))
+  (set-count
+   (apply set-intersect
+          (map (compose list->set string->list) answers))))
+
+(define (part2 filename)
+  (apply + (map count-intersection (read-input filename))))
+
+(module+ test
+  (check-equal? (part2 "test") 6))
+
+(module+ main
+  (displayln (part2 "input")))

2020/day06/test

@@ -0,0 +1,15 @@
+abc
+
+a
+b
+c
+
+ab
+ac
+
+a
+a
+a
+a
+
+b