Initial commit

2020/day02/day02.c

@@ -0,0 +1,45 @@
+#include <stdbool.h>
+#include <stdio.h>
+
+bool is_valid_part1(int lower, int upper, char key, char *pass) {
+  int count = 0;
+  for (char *c = pass; *c != 0; ++c) {
+    if (*c == key) {
+      count++;
+    }
+  }
+  return (count >= lower) && (count <= upper);
+}
+
+bool is_valid_part2(int pos1, int pos2, char key, char *pass) {
+  return (pass[pos1 - 1] == key) ^ (pass[pos2 - 1] == key);
+}
+
+int main(int argc, char *argv[]) {
+  if (argc < 2) {
+    printf("Usage: %s <input file>\n", argv[0]);
+    return 0;
+  }
+  FILE *input = fopen(argv[1], "r");
+
+  int lower, upper;
+  char key;
+  char pass[256];
+
+  int count1 = 0;
+  int count2 = 0;
+
+  while (fscanf(input, "%d-%d %c: %s", &lower, &upper, &key, pass) == 4) {
+    if (is_valid_part1(lower, upper, key, pass)) {
+      count1++;
+    }
+    if (is_valid_part2(lower, upper, key, pass)) {
+      count2++;
+    }
+  }
+
+  printf("Part 1: %d\n", count1);
+  printf("Part 2: %d\n", count2);
+
+  return 0;
+}

2020/day02/day02.dyalog

@@ -0,0 +1,3 @@
+ p←↑¨{⍵⊆⍨~⍵∊':- '}¨⊃⎕NGET'input'1
+ +/{((⍎1⌷⍵),1+⍎2⌷⍵)(1=⍸)+/(⊃3⌷⍵)⍷4⌷⍵}¨p  ⍝ Part 1
+ +/{≠/(⊃3⌷⍵)=(4⌷⍵)[⍎¨↓(⊂1 2)⌷⍵]}¨p  ⍝ Part 2

2020/day02/day02.rkt

@@ -0,0 +1,61 @@
+#lang racket
+
+(module+ test
+  (require rackunit))
+
+(module+ main
+  (displayln "Day 2"))
+
+(struct policy
+  (lower upper char)
+  #:transparent)
+
+(define (parse-line str)
+  (define lst (string-split str #px"(\\s+|:\\s+|-)"))
+  (values (policy (string->number (first lst))
+                  (string->number (second lst))
+                  (car (string->list (third lst))))
+          (last lst)))
+
+(define (read-input filename)
+  (with-input-from-file filename
+    (lambda ()
+      (for/lists (policies passwords)
+                 ([line (in-lines)])
+        (parse-line line)))))
+
+(define (valid? pol pass)
+  (define cnt (count (λ (x) (equal? x (policy-char pol)))
+                     (string->list pass)))
+  (and (<= (policy-lower pol) cnt)
+       (>= (policy-upper pol) cnt)))
+
+(define (part1 filename)
+  (define-values (policies passwords) (read-input filename))
+  (for/sum ([pol policies]
+            [pass passwords]
+            #:when (valid? pol pass))
+    1))
+
+(module+ test
+  (check-equal? (part1 "test") 2))
+
+(module+ main
+  (displayln (part1 "input")))
+
+(define (new-valid? pol pass)
+  (xor (equal? (string-ref pass (sub1 (policy-lower pol))) (policy-char pol))
+       (equal? (string-ref pass (sub1 (policy-upper pol))) (policy-char pol))))
+
+(define (part2 filename)
+  (define-values (policies passwords) (read-input filename))
+  (for/sum ([pol policies]
+            [pass passwords]
+            #:when (new-valid? pol pass))
+    1))
+
+(module+ test
+  (check-equal? (part2 "test") 1))
+
+(module+ main
+  (displayln (part2 "input")))

2020/day02/test

@@ -0,0 +1,3 @@
+1-3 a: abcde
+1-3 b: cdefg
+2-9 c: ccccccccc