Data commit

Task/Paraffins/Nim/paraffins.nim

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+import bigints
+
+const
+  nMax: int32 = 250
+  nBranches = 4
+
+var rooted, unrooted: array[nMax + 1, BigInt]
+rooted[0..1] = [1.initBigInt, 1.initBigInt]
+unrooted[0..1] = [1.initBigInt, 1.initBigInt]
+for i in 2 .. nMax:
+  rooted[i] = 0.initBigInt
+  unrooted[i] = 0.initBigInt
+
+proc choose(m: BigInt; k: int32): BigInt =
+  result = m
+  if k == 1: return
+  for i in 1 ..< k:
+    result = result * (m + i) div (i + 1)
+
+proc tree(br, n, l, sum: int32; cnt: BigInt) =
+  var s: int32 = 0
+  for b in br + 1 .. nBranches:
+    s = sum + (b - br) * n
+    if s > nMax: return
+
+    let c = choose(rooted[n], b - br) * cnt
+
+    if l * 2 < s: unrooted[s] += c
+    if b == nBranches: return
+    rooted[s] += c
+    for m in countdown(n-1, 1):
+      tree b, m, l, s, c
+
+proc bicenter(s: int32) =
+  if (s and 1) == 0:
+    unrooted[s] += rooted[s div 2] * (rooted[s div 2] + 1) div 2
+
+for n in 1 .. nMax:
+  tree 0, n, n, 1, 1.initBigInt
+  n.bicenter
+  echo n, ": ", unrooted[n]