Data commit

Task/Eban-numbers/Nim/eban-numbers-1.nim

@@ -0,0 +1,55 @@
+import strformat
+
+proc iseban(n: int): bool =
+  if n == 0:
+    return false
+  var b = n div 1_000_000_000
+  var r = n mod 1_000_000_000
+  var m = r div 1_000_000
+  r = r mod 1_000_000
+  var t = r div 1_000
+  r = r mod 1_000
+  m = if m in 30..66: m mod 10 else: m
+  t = if t in 30..66: t mod 10 else: t
+  r = if r in 30..66: r mod 10 else: r
+  return {b, m, t, r} <= {0, 2, 4, 6}
+
+echo "eban numbers up to and including 1000:"
+for i in 0..100:
+  if iseban(i):
+    stdout.write(&"{i} ")
+
+echo "\n\neban numbers between 1000 and 4000 (inclusive):"
+for i in 1_000..4_000:
+  if iseban(i):
+    stdout.write(&"{i} ")
+
+var count = 0
+for i in 0..10_000:
+  if iseban(i):
+    inc count
+echo &"\n\nNumber of eban numbers up to and including {10000:8}: {count:4}"
+
+count = 0
+for i in 0..100_000:
+  if iseban(i):
+    inc count
+echo &"\nNumber of eban numbers up to and including {100000:8}: {count:4}"
+
+count = 0
+for i in 0..1_000_000:
+  if iseban(i):
+    inc count
+echo &"\nNumber of eban numbers up to and including {1000000:8}: {count:4}"
+
+count = 0
+for i in 0..10_000_000:
+  if iseban(i):
+    inc count
+echo &"\nNumber of eban numbers up to and including {10000000:8}: {count:4}"
+
+count = 0
+for i in 0..100_000_000:
+  if iseban(i):
+    inc count
+echo &"\nNumber of eban numbers up to and including {100000000:8}: {count:4}"

Task/Eban-numbers/Nim/eban-numbers-2.nim

@@ -0,0 +1,44 @@
+import math, strutils, strformat
+
+#---------------------------------------------------------------------------------------------------
+
+func ebanCount(p10: Natural): Natural =
+  ## Return the count of eban numbers 1..10^p10.
+  let
+    n = p10 - p10 div 3
+    p5 = n div 2
+    p4 = (n + 1) div 2
+  result = 5^p5 * 4^p4 - 1
+
+#---------------------------------------------------------------------------------------------------
+
+func eban(n: Natural): bool =
+  ## Return true if n is an eban number (only fully tested to 10e9).
+  if n == 0: return false
+  var n = n
+  while n != 0:
+    let thou = n mod 1000
+    if thou div 100 != 0: return false
+    if thou div 10 notin {0, 3, 4, 5, 6}: return false
+    if thou mod 10 notin {0, 2, 4, 6}: return false
+    n = n div 1000
+  result = true
+
+#———————————————————————————————————————————————————————————————————————————————————————————————————
+
+var s: seq[Natural]
+for i in 0..1000:
+  if eban(i): s.add(i)
+echo fmt"Eban to 1000: {s.join("", "")} ({s.len} items)"
+
+s.setLen(0)
+for i in 1000..4000:
+  if eban(i): s.add(i)
+echo fmt"Eban 1000..4000: {s.join("", "")} ({s.len} items)"
+
+import times
+let t0 = getTime()
+for i in 0..21:
+  echo fmt"ebanCount(10^{i}): {ebanCount(i)}"
+echo ""
+echo fmt"Time: {getTime() - t0}"