Frist psot

.gitignore

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+*~

p77.lisp

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+(defun prime-sum-count (n primes)
+  (let ((primes-descending (reverse primes)))
+    (labels ((recurse (primes target)
+	       (cond ((= target 0) 1)
+		     ((< target 0) 0)
+		     ((null primes) 0)
+		     (t (+ (recurse primes (- target (first primes)))
+			   (recurse (rest primes) target))))))
+      (recurse primes-descending n))))
+
+(defun p77 (&key (ways 5000) (prime-count 1000))
+  (let ((primes (get-primes prime-count)))
+    (loop for n upfrom 1
+	  for count = (prime-sum-count n primes)
+	  until (> count ways)
+	  finally (return n))))

shared.lisp

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+(defun get-primes (max)
+  (let ((primes nil)
+	(composites (make-array (1+ max) :initial-element 0)))
+    (loop for n from 2 upto max
+	  do (when (= 0 (aref composites n))
+	       (push n primes)
+	       (loop for m from (* 2 n) upto max by n
+		     do (incf (aref composites m)))))
+    (nreverse primes)))