63 lines
1.6 KiB
Factor
63 lines
1.6 KiB
Factor
! Copyright (c) 2007 Samuel Tardieu, Aaron Schaefer.
|
|
! See http://factorcode.org/license.txt for BSD license.
|
|
USING: io.files math.parser namespaces project-euler.common
|
|
io.encodings.ascii sequences splitting ;
|
|
IN: project-euler.067
|
|
|
|
! http://projecteuler.net/index.php?section=problems&id=67
|
|
|
|
! DESCRIPTION
|
|
! -----------
|
|
|
|
! By starting at the top of the triangle below and moving to adjacent numbers
|
|
! on the row below, the maximum total from top to bottom is 23.
|
|
|
|
! 3
|
|
! 7 5
|
|
! 2 4 6
|
|
! 8 5 9 3
|
|
|
|
! That is, 3 + 7 + 4 + 9 = 23.
|
|
|
|
! Find the maximum total from top to bottom in triangle.txt (right click and
|
|
! 'Save Link/Target As...'), a 15K text file containing a triangle with
|
|
! one-hundred rows.
|
|
|
|
! NOTE: This is a much more difficult version of Problem 18. It is not possible
|
|
! to try every route to solve this problem, as there are 2^99 altogether! If you
|
|
! could check one trillion (10^12) routes every second it would take over twenty
|
|
! billion years to check them all. There is an efficient algorithm to solve it. ;o)
|
|
|
|
|
|
! SOLUTION
|
|
! --------
|
|
|
|
! Propagate from bottom to top the longest cumulative path as is done in
|
|
! problem 18.
|
|
|
|
<PRIVATE
|
|
|
|
: source-067 ( -- seq )
|
|
"resource:extra/project-euler/067/triangle.txt"
|
|
ascii file-lines [ " " split [ string>number ] map ] map ;
|
|
|
|
PRIVATE>
|
|
|
|
: euler067 ( -- answer )
|
|
source-067 propagate-all first first ;
|
|
|
|
! [ euler067 ] 100 ave-time
|
|
! 18 ms run / 0 ms GC time
|
|
|
|
|
|
! ALTERNATE SOLUTIONS
|
|
! -------------------
|
|
|
|
: euler067a ( -- answer )
|
|
source-067 max-path ;
|
|
|
|
! [ euler067a ] 100 ave-time
|
|
! 14 ms run / 0 ms GC ave time - 100 trials
|
|
|
|
MAIN: euler067a
|