239 lines
8.8 KiB
Nim
239 lines
8.8 KiB
Nim
import ./common, std/[sequtils, algorithm, sugar, sets, strformat, strutils, tables, options, json]
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type
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BinaryTreeNodePathSegment = enum left, right
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BinaryTreeNodePath = seq[BinaryTreeNodePathSegment]
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BinaryTreeNodeKind = enum
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leaf
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branch
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BinaryTreeNode = ref BinaryTreeNodeObj
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BinaryTreeNodeObj = object
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case kind: BinaryTreeNodeKind
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of leaf: value: uint64
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of branch: left, right: BinaryTreeNode
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BinaryTreeNodeParseResult = object
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node: BinaryTreeNodeObj
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parsed_length: uint64
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proc parseBinaryTree(s: string): (BinaryTreeNode, uint64) =
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case s[0]:
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of '0'..'9': result = (BinaryTreeNode(kind: leaf, value: uint8(s[0]) - uint8('0')), 1'u64)
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of '[':
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let (left, leftLen) = parseBinaryTree(s[1..^1])
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let (right, righLen) = parseBinaryTree(s[2+leftLen..^1])
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result = (BinaryTreeNode(kind: branch, left: left, right: right), 3'u64 + leftLen + righLen)
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else:
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echo "unexpected string"
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proc `$`(node: BinaryTreeNode): string =
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case node.kind:
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of leaf: result = $node.value
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of branch: result = &"[{$node.left},{$node.right}]"
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when not defined(release):
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block:
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let (bt, n) = parseBinaryTree("[[1,2],3]")
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assert bt.right.value == 3'u64
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assert bt.left.left.value == 1'u64
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assert bt.left.right.value == 2'u64
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assert n == 9
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proc nodeAt(node: BinaryTreeNode, path: BinaryTreeNodePath): Option[BinaryTreeNode] =
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var curNode = node
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for p in path:
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if curNode.kind == leaf: return none(BinaryTreeNode)
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case p:
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of left: curNode = curNode.left
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of right: curNode = curNode.right
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return some(curNode)
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when not defined(release):
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block:
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let (bt, _) = parseBinaryTree("[[1,2],3]")
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let n = bt.nodeAt(@[right]).get
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assert n.kind == leaf
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assert n.value == 3
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let n2 = bt.nodeAt(@[left]).get
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assert n2.kind == branch
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assert n2.left.value == 1
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assert n2.right.value == 2
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let n3 = bt.nodeAt(@[left, right]).get
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assert n3.kind == leaf
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assert n3.value == 2
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let n4 = bt.nodeAt(@[left, left]).get
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assert n4.kind == leaf
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assert n4.value == 1
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let (bt2, _) = parseBinaryTree("[[[[[8,[1,2]],3],4],7],6]")
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let n5 = bt2.nodeAt(@[left, left, left, left, left]).get()
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assert n5.value == 8
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let n6 = bt2.nodeAt(@[left, left, left, left, right, left]).get()
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assert n6.value == 1
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proc updateNode(node: var BinaryTreeNode, path: BinaryTreeNodePath, callback: (BinaryTreeNode) -> BinaryTreeNode) =
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var curNode = node
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var walker = path.reversed()
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while walker.len() > 1:
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case walker.pop():
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of left: curNode = curNode.left
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of right: curNode = curNode.right
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# TODO: handle empty path?
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case walker.pop():
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of left: curNode.left = callback(curNode.left)
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of right: curNode.right = callback(curNode.right)
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when not defined(release):
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block:
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var (bt, _) = parseBinaryTree("[[1,2],3]")
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bt.updateNode(@[left], (_) => BinaryTreeNode(kind: leaf, value: 4'u64))
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assert bt.left.kind == leaf
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assert bt.left.value == 4
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assert bt.right.kind == leaf
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assert bt.right.value == 3
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proc crawlFor(node: BinaryTreeNode, predicate: (node: BinaryTreeNode, path: BinaryTreeNodePath) -> bool, path: BinaryTreeNodePath = @[], preferredSide: BinaryTreeNodePathSegment = left): Option[BinaryTreeNodePath] =
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if node.predicate(path):
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return some(path)
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elif node.kind == branch:
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if preferredSide == left:
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let ln = node.left.crawlFor(predicate, path & @[left], preferredSide)
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if ln.isSome: return ln
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let rn = node.right.crawlFor(predicate, path & @[right], preferredSide)
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if rn.isSome: return rn
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else:
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let rn = node.right.crawlFor(predicate, path & @[right], preferredSide)
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if rn.isSome: return rn
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let ln = node.left.crawlFor(predicate, path & @[left], preferredSide)
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if ln.isSome: return ln
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return none(BinaryTreeNodePath)
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when not defined(release):
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block:
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var (bt, _) = parseBinaryTree("[[1,2],3]")
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assert bt.crawlFor((_, p) => p.len() > 4).isNone
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var (bt2, _) = parseBinaryTree("[[[[[9,8],1],2],3],8]")
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var p = bt2.crawlFor((n, p) => p.len() > 4 and n.kind == leaf and n.value == 8'u64, @[], right)
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assert p.isSome
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assert p.get == @[left, left, left, left, right]
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proc valueLeftOf(node: BinaryTreeNode, path: BinaryTreeNodePath): Option[BinaryTreeNodePath] =
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var walker = path
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while walker.len > 0:
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if walker.pop == right:
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let subPath = walker & @[left]
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let subNode = node.nodeAt(subPath)
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if subNode.isSome:
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let candidatePath = subNode.get.crawlFor((n, _) => n.kind == leaf, @[], right)
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if candidatePath.isSome: return some(subPath & candidatePath.get)
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# echo &"No lefter value node"
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return none(BinaryTreeNodePath)
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when not defined(release):
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block:
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let (bt, _) = parseBinaryTree("[[1,2],3]")
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assert bt.valueLeftOf(@[right]) == some(@[left, right])
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assert bt.valueLeftOf(@[left, left]) == none(BinaryTreeNodePath)
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assert bt.valueLeftOf(@[left, right]) == some(@[left, left])
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let (bt2, _) = parseBinaryTree("[1,[2,3]]")
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assert bt2.valueLeftOf(@[right, right]) == some(@[right, left])
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assert bt2.valueLeftOf(@[right, left]) == some(@[left])
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proc valueRightOf(node: BinaryTreeNode, path: BinaryTreeNodePath): Option[BinaryTreeNodePath] =
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var walker = path
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while walker.len > 0:
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if walker.pop == left:
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let subPath = walker & @[right]
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let subNode = node.nodeAt(subPath)
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if subNode.isSome:
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let candidatePath = subNode.get.crawlFor((n, _) => n.kind == leaf, @[], left)
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if candidatePath.isSome: return some(subPath & candidatePath.get)
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# echo &"No righter value node"
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return none(BinaryTreeNodePath)
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proc isExplodeCandidate(n: BinaryTreeNode, p: BinaryTreeNodePath): bool =
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((p.len() >= 4) and (n.kind == branch) and (n.left.kind == leaf) and (n.right.kind == leaf))
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proc doExplode(node: var BinaryTreeNode): bool =
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let explodePath = node.crawlFor(isExplodeCandidate)
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if explodePath.isSome:
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let explodingPair = node.nodeAt(explodePath.get).get
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let lp = node.valueLeftOf(explodePath.get)
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let rp = node.valueRightOf(explodePath.get)
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if lp.isSome:
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node.updateNode(lp.get, (n) => BinaryTreeNode(kind: leaf, value: n.value + explodingPair.left.value))
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if rp.isSome:
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node.updateNode(rp.get, (n) => BinaryTreeNode(kind: leaf, value: n.value + explodingPair.right.value))
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node.updateNode(explodePath.get, (_) => BinaryTreeNode(kind: leaf, value: 0))
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explodePath.isSome
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when not defined(release):
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block:
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var (bt, _) = parseBinaryTree("[[[[[9,8],1],2],3],4]")
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let didExplode = bt.doExplode
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assert didExplode == true
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assert bt.left.left.left.left.kind == leaf
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assert bt.left.left.left.left.value == 0
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proc splitAt(node: var BinaryTreeNode, path: BinaryTreeNodePath) =
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let splittingValue = node.nodeAt(path).get
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let lv = splittingValue.value div 2
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let rv = lv + (splittingValue.value mod 2)
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node.updateNode(path, (_) => BinaryTreeNode(
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kind: branch,
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left: BinaryTreeNode(kind: leaf, value: lv),
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right: BinaryTreeNode(kind: leaf, value: rv),
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))
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proc doSplit(node: var BinaryTreeNode): bool =
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let splitPath = node.crawlFor((n, _) => n.kind == leaf and n.value >= 10)
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if splitPath.isSome: node.splitAt splitPath.get
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splitPath.isSome
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proc magnitude(node: BinaryTreeNode): uint64 =
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case node.kind:
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of leaf: node.value
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else: (3 * node.left.magnitude) + (2 * node.right.magnitude)
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proc reduceTree(bt: var BinaryTreeNode) =
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while true:
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if bt.doExplode: continue
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if bt.doSplit: continue
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break
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proc `+`(addend1: BinaryTreeNode, addend2: BinaryTreeNode): BinaryTreeNode =
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result = BinaryTreeNode(kind: branch, left: addend1, right: addend2)
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result.reduceTree()
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when not defined(release):
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block:
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var (bt1, _) = parseBinaryTree("[[2,[[7,7],7]],[[5,8],[[9,3],[0,2]]]]")
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assert $bt1 == "[[2,[[7,7],7]],[[5,8],[[9,3],[0,2]]]]"
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var (bt2, _) = parseBinaryTree("[[[0,[5,8]],[[1,7],[9,6]]],[[4,[1,2]],[[1,4],2]]]")
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var a = bt1 + bt2
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assert $a == "[[[[7,8],[6,6]],[[6,0],[7,7]]],[[[7,8],[8,8]],[[7,9],[0,6]]]]"
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proc p1(input: Lines): uint64 =
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input.mapIt(it.parseBinaryTree[0]).foldl(a + b).magnitude
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proc p2(input: Lines): uint64 =
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for i,p1 in input.pairs:
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for j,p2 in input.pairs:
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if i == j: continue
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let (b1, _) = p1.parseBinaryTree
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let (b2, _) = p2.parseBinaryTree
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let a = b1 + b2
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let m = a.magnitude
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result = max(m, result)
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const input = """
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[[[0,[5,8]],[[1,7],[9,6]]],[[4,[1,2]],[[1,4],2]]]
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[[[5,[2,8]],4],[5,[[9,9],0]]]
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[6,[[[6,2],[5,6]],[[7,6],[4,7]]]]
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[[[6,[0,7]],[0,9]],[4,[9,[9,0]]]]
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[[[7,[6,4]],[3,[1,3]]],[[[5,5],1],9]]
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[[6,[[7,3],[3,2]]],[[[3,8],[5,7]],4]]
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[[[[5,4],[7,7]],8],[[8,3],8]]
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[[9,3],[[9,9],[6,[4,9]]]]
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[[2,[[7,7],7]],[[5,8],[[9,3],[0,2]]]]
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[[[[5,2],5],[8,[3,7]]],[[5,[7,5]],[4,4]]]
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""".strip().split('\n').mapIt(it.strip)
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doDayX 18, (n: int) => n.loadInput, p1, p2, (input, 4140'u64, 3993'u64)
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