2016 Update

Task/N-queens-problem/Julia/n-queens-problem-1.julia

@@ -0,0 +1,77 @@
+#!/usr/bin/env julia
+
+__precompile__(true)
+
+"""
+# EightQueensPuzzle
+
+Ported to **Julia** from examples in several languages from
+here: https://hbfs.wordpress.com/2009/11/10/is-python-slow
+"""
+module EightQueensPuzzle
+
+export main
+
+type Board
+    cols::Int
+    nodes::Int
+    diag45::Int
+    diag135::Int
+    solutions::Int
+
+    Board() = new(0, 0, 0, 0, 0)
+end
+
+"Marks occupancy."
+function mark!(b::Board, k::Int, j::Int)
+    b.cols    $= (1 << j)
+    b.diag135 $= (1 << (j+k))
+    b.diag45  $= (1 << (32+j-k))
+end
+
+"Tests if a square is menaced."
+function test(b::Board, k::Int, j::Int)
+    b.cols    & (1 << j)        +
+    b.diag135 & (1 << (j+k))    +
+    b.diag45  & (1 << (32+j-k)) == 0
+end
+
+"Backtracking solver."
+function solve!(b::Board, niv::Int, dx::Int)
+    if niv > 0
+        for i in 0:dx-1
+            if test(b, niv, i) == true
+                mark!(b, niv, i)
+                solve!(b, niv-1, dx)
+                mark!(b, niv, i)
+            end
+        end
+    else
+        for i in 0:dx-1
+            if test(b, 0, i) == true
+                b.solutions += 1
+            end
+        end
+    end
+    b.nodes += 1
+    b.solutions
+end
+
+"C/C++-style `main` function."
+function main()
+    for n = 1:17
+        gc()
+        b = Board()
+        @show n
+        print("elapsed:")
+        solutions = @time solve!(b, n-1, n)
+        @show solutions
+        println()
+    end
+end
+
+end
+
+using  EightQueensPuzzle
+
+main()

Task/N-queens-problem/Julia/n-queens-problem-2.julia

@@ -0,0 +1,68 @@
+juser@juliabox:~$ /opt/julia-0.5/bin/julia eight_queen_puzzle.jl
+n = 1
+elapsed:  0.000001 seconds
+solutions = 1
+
+n = 2
+elapsed:  0.000001 seconds
+solutions = 0
+
+n = 3
+elapsed:  0.000001 seconds
+solutions = 0
+
+n = 4
+elapsed:  0.000001 seconds
+solutions = 2
+
+n = 5
+elapsed:  0.000003 seconds
+solutions = 10
+
+n = 6
+elapsed:  0.000008 seconds
+solutions = 4
+
+n = 7
+elapsed:  0.000028 seconds
+solutions = 40
+
+n = 8
+elapsed:  0.000108 seconds
+solutions = 92
+
+n = 9
+elapsed:  0.000463 seconds
+solutions = 352
+
+n = 10
+elapsed:  0.002146 seconds
+solutions = 724
+
+n = 11
+elapsed:  0.010646 seconds
+solutions = 2680
+
+n = 12
+elapsed:  0.057603 seconds
+solutions = 14200
+
+n = 13
+elapsed:  0.334600 seconds
+solutions = 73712
+
+n = 14
+elapsed:  2.055078 seconds
+solutions = 365596
+
+n = 15
+elapsed: 13.480449 seconds
+solutions = 2279184
+
+n = 16
+elapsed: 97.192552 seconds
+solutions = 14772512
+
+n = 17
+elapsed:720.314676 seconds
+solutions = 95815104