Add day trois

3/GNUmakefile

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+# -*- makefile-gmake -*-
+include ../gnu.mk

3/main.scm

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+(import (scheme base)
+        (scheme char)
+        (scheme cxr)
+        (scheme file)
+        (scheme process-context)
+        (scheme write))
+
+(define (max-joltage line batteries)
+  (let ((lst (map digit-value (string->list line))))
+    (let loop ((req-tail-length (- batteries 1))
+               (lst lst)
+               (sum 0))
+      (if (negative? req-tail-length)
+          sum
+          ;; this is O^one million at least
+          (let ((m (memq (apply max (reverse (list-tail (reverse lst) req-tail-length))) lst)))
+            (loop (- req-tail-length 1) (cdr m) (+ (* sum 10) (car m))))))))
+
+(define (part file batteries)
+  (with-input-from-file file
+    (lambda ()
+      (let loop ((line (read-line))
+                 (sum 0))
+        (if (eof-object? line)
+            (begin
+              (display (number->string sum))
+              (newline))
+            (loop (read-line) (+ sum (max-joltage line batteries))))))))
+
+(for-each (lambda (file) (part file 2)) (cdr (command-line)))
+(for-each (lambda (file) (part file 12)) (cdr (command-line)))

3/makefile

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+# -*- makefile-bsdmake -*-
+# Disable Skint because no numerical tower
+SCHEMES=chibi chicken gauche guile racket sagittarius
+.include "../common.mk"