1 files changed, 63 insertions, 0 deletions
diff --git a/challenge-125/stuart-little/lua/ch-2.lua b/challenge-125/stuart-little/lua/ch-2.lua
new file mode 100755
index 0000000000..78dc34273c
--- /dev/null
+++ b/challenge-125/stuart-little/lua/ch-2.lua
@@ -0,0 +1,63 @@
+#!/usr/bin/env lua
+
+function maxBy(fn,t)
+   local mx,val = -math.huge,nil
+   for k,v in ipairs(t) do
+      if fn(v,k,t) > mx then
+	 mx = fn(v,k,t)
+	 val = v
+      end
+   end
+   return val
+end
+
+function lr(tree) 
+   if #tree < 3 or tree[1] == '.' then return {{},{}} end
+   if #tree == 3 then return {{"."},{"."}} end
+   local left={}
+   local sm,ix = 0,2
+   while (sm ~= -1) do
+      table.insert(left,tree[ix])
+      sm = sm+(tree[ix] == '.' and -1 or 1)
+      ix = ix+1
+   end
+   return {left,table.pack(table.unpack(tree, #left+2))}
+end
+
+function lrLongPath(tree) 
+   if tree[1] == '.' then return {{},{}} end
+   if #tree == 3 then return {{tree[1]},{tree[1]}} end
+   local left,right = table.unpack(lr(tree))
+   local lPath = table.pack(tree[1], table.unpack(maxBy(function(v,k,t) return #v end, lrLongPath(left))))
+   local rPath = table.pack(tree[1], table.unpack(maxBy(function(v,k,t) return #v end, lrLongPath(right))))
+   return {lPath,rPath}
+end
+
+function biLongPath(tree) 
+   if #tree < 3 or tree[1] == '.' then return {} end
+   if #tree == 3 then return {tree[1]} end
+   local lPath,path = table.unpack(lrLongPath(tree))
+   for i=2,#lPath do table.insert(path,1,lPath[i]) end   
+   local left,right = table.unpack(lr(tree))
+   return maxBy(function(v,k,t) return #v end, {path, biLongPath(left), biLongPath(right)})
+end
+
+print(table.unpack(biLongPath(arg)))
+
+--[[
+run <script> <tree in preorder form with '.' for empty nodes, entered as space-separated values>
+
+ref: https://stackoverflow.com/a/2676849/11064961
+
+e.g. 1 2 4 . 7 . . . 3 5 . . 6 . . represents the tree
+
+        1
+       / \
+      2   3
+     /   / \
+    4   5   6
+     \
+      7
+
+given as an example in the problem formulation at https://perlweeklychallenge.org/blog/perl-weekly-challenge-113/#TASK2
+--]]