add old solutions

1 files changed, 30 insertions, 0 deletions

diff --git a/2.lua b/2.lua
new file mode 100644
index 0000000..d70cdc3
--- /dev/null
+++ b/2.lua
@@ -0,0 +1,30 @@
+local function memoize(fn)
+    local t = {}
+    return function(x)
+        local y = t[x]
+        if y == nil then y = fn(x); t[x] = y end
+        return y
+    end
+end
+
+fib = memoize(function(n)
+    if n < 3 then return 1 end
+    return fib(n - 1) + fib(n - 2)
+end)
+
+local root5 = math.sqrt(5)
+local phi = (1 + root5)/2
+local function fib2(n)
+    return math.floor((phi^n-(1-phi)^n)/root5+0.5)
+end
+
+local sum = 0
+local i = 0
+while true do
+    i = i + 1
+    local n = fib(i)
+    if n > 1000000 then break end
+    if n % 2 == 0 then sum = sum + n end
+end
+
+print(sum)