initial commit

1 files changed, 28 insertions, 0 deletions

diff --git a/euler14.scm b/euler14.scm
new file mode 100644
index 0000000..3adc07a
--- /dev/null
+++ b/euler14.scm
@@ -0,0 +1,28 @@
+(define (chainlen n)
+ (define (next m)
+  (if (even? m)
+   (/ m 2)
+   (+ (* m 3) 1)))
+ (define (count-iter cur cnt)
+  (if (= cur 1)
+   cnt
+   (count-iter (next cur) (+ cnt 1))))
+ (count-iter n 1))
+
+(define (find-max-len-start limit)
+  (define (try cur longest ans)
+	(cond ((> cur limit) ans)
+		  ((= (remainder (- cur 4) 6) 0)
+		   ;it's even and is 3n+1=>it's 6n+4
+		   (try (+ cur 1) longest ans))
+		  (else
+			(let ((len (chainlen cur))
+				  (curn (+ cur 1)))
+			  (if (> len longest)
+				(try curn len cur)
+				(try curn longest ans))))))
+ (let ((lowest (ceiling (/ limit 2))))
+  (try lowest 1 lowest)))
+
+(display (find-max-len-start 999999))
+(newline)