Merge remote-tracking branch 'upstream/master'

2 files changed, 174 insertions, 0 deletions

diff --git a/challenge-109/abigail/lua/ch-1.lua b/challenge-109/abigail/lua/ch-1.lua
new file mode 100644
index 0000000000..74c3b7d914
--- /dev/null
+++ b/challenge-109/abigail/lua/ch-1.lua
@@ -0,0 +1,43 @@
+#!/opt/local/bin/lua
+
+--
+-- See ../README.md
+--
+
+--
+-- Run as: lua ch-1.lua [plain | compute]
+--
+
+local PLAIN   =  0
+local COMPUTE =  1
+
+local COUNT   = 20
+
+function divisor_sum (n)
+    local sum = 0
+    for i = 2, n / 2 do
+        if   n % i == 0 
+        then sum = sum + i
+        end
+    end
+    return (sum)
+end
+
+local type = PLAIN
+if   #arg >= 1 and arg [1] == "compute"
+then type = COMPUTE
+end
+
+if   type == PLAIN
+then print ("0, 0, 0, 2, 0, 5, 0, 6, 3, 7, 0, 15, 0, 9, 8, 14, 0, 20, 0, 21")
+end
+
+if   type == COMPUTE
+then for n = 1, COUNT do
+         if n > 1 
+         then io . write (", ")
+         end
+         io . write (divisor_sum (n))
+     end
+     io . write ("\n")
+end
diff --git a/challenge-109/abigail/lua/ch-2.lua b/challenge-109/abigail/lua/ch-2.lua
new file mode 100644
index 0000000000..2b40532bfc
--- /dev/null
+++ b/challenge-109/abigail/lua/ch-2.lua
@@ -0,0 +1,131 @@
+#!/opt/local/bin/lua
+
+--
+-- See ../README.md
+--
+
+--
+-- Run as: lua ch-2.lua < input-file
+--
+
+local SIZE = 7
+
+for line in io . lines () do
+    local numbers = {}
+    for n in line : gmatch ("-?%d+") do
+        numbers [#numbers + 1] = tonumber (n)
+    end
+
+    --
+    -- Initialize the a differences table.
+    --
+    local differences = {}
+    for n_i, n in pairs (numbers) do
+        differences [n] = {}
+    end
+
+    -- 
+    -- Find all the differences; store the indices of the
+    -- pairs of numbers giving the difference. Ignore a difference
+    -- which is not present in the numbers array.
+    --
+    for i = 1, SIZE do
+        for j = i + 1, SIZE do
+            local diff = numbers [i] - numbers [j]
+            if   differences [ diff] ~= nil
+            then table . insert (differences [ diff], {i, j})
+            end
+            if   differences [-diff] ~= nil
+            then table . insert (differences [-diff], {j, i})
+            end
+        end
+    end
+
+    --
+    -- For each possible value d, find the pairs of differences
+    -- equal to d, such that all five numbers are difference.
+    --
+
+    for d_i = 1, SIZE do
+        local d     = numbers [d_i]
+        local diffs = differences [d]
+
+        for x = 1, #diffs do
+            --
+            -- Ignore any difference involving d_i
+            --
+            if   diffs [x] [1] == d_i or diffs [x] [2] == d_i
+            then goto end_x
+            end
+            for y = x + 1, #diffs do
+                --
+                -- Second difference cannot involve the number at d_i,
+                -- and the indices involved in the second difference
+                -- must be different from the first difference.
+                --
+                if   diffs [y] [1] == d_i or diffs [y] [2] == d_i or
+                     diffs [x] [1] ==        diffs [y] [1]        or
+                     diffs [x] [1] ==        diffs [y] [2]        or
+                     diffs [x] [2] ==        diffs [y] [1]        or
+                     diffs [x] [2] ==        diffs [y] [2]
+                then goto end_y
+                end
+
+                --
+                -- W.l.o.g. we can now assume diffs [x] are
+                -- the indices for a and c, and diffs [y]
+                -- are the indices for g and e.
+                --
+                local a_i = diffs [x] [1]
+                local c_i = diffs [x] [2]
+                local g_i = diffs [y] [1]
+                local e_i = diffs [y] [2]
+
+                --
+                -- Try the remaining indices for b_i and f_i
+                --
+                for b_i = 1, SIZE do
+                    if   b_i == a_i or b_i == c_i or b_i == d_i or
+                         b_i == e_i or b_i == g_i
+                    then goto end_bi
+                    end
+                    for f_i = 1, SIZE do
+                        if   f_i == a_i or f_i == b_i or f_i == c_i or
+                             f_i == d_i or f_i == e_i or f_i == g_i
+                        then goto end_fi
+                        end
+                        --
+                        -- Do we have a winner?
+                        --
+                        local target = numbers [a_i] + numbers [b_i]
+                        if   target == numbers [b_i] + numbers [c_i] +
+                                       numbers [d_i]   and
+                             target == numbers [d_i] + numbers [e_i] +
+                                       numbers [f_i]   and
+                             target == numbers [f_i] + numbers [g_i]
+                        then --
+                             -- We have a winner. Print it, and its reverse
+                             --
+                             io . write (
+                                  string . format ("%d %d %d %d %d %d %d\n",
+                                           numbers [a_i], numbers [b_i],
+                                           numbers [c_i], numbers [d_i],
+                                           numbers [e_i], numbers [f_i],
+                                           numbers [g_i]))
+                             io . write (
+                                  string . format ("%d %d %d %d %d %d %d\n",
+                                           numbers [g_i], numbers [f_i],
+                                           numbers [e_i], numbers [d_i],
+                                           numbers [c_i], numbers [b_i],
+                                           numbers [a_i]))
+                        end
+                        ::end_fi::
+                    end
+                    ::end_bi::
+                end
+                ::end_y::
+            end
+            ::end_x::
+        end
+    end
+end