91 lines
3.4 KiB
Nim
91 lines
3.4 KiB
Nim
import ./common, std/[sequtils, algorithm, sugar, sets, strformat, strutils, tables, options]
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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 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 = node.left
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of right: curNode = node.left
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return some(curNode)
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proc crawlFor(node: BinaryTreeNode, predicate: (node: BinaryTreeNode, path: BinaryTreeNodePath) -> bool, path: BinaryTreeNodePath = @[]): Option[BinaryTreeNodePath] =
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if node.predicate(path): return some(path)
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elif node.kind == branch:
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let lp = path & @[left]
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let ln = node.left.crawlFor(predicate, lp)
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if ln.isSome: return some(lp)
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let rp = path & @[right]
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let rn = node.right.crawlFor(predicate, rp)
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if rn.isSome: return some(rp)
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return none(BinaryTreeNodePath)
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when not defined(release):
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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 valueLeftOf(node: var BinaryTreeNode, path: BinaryTreeNodePath): Option[BinaryTreeNodePath] =
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# for every right in the given path ordered from deepest to shallowest
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# go left at that point and find the right-most value if any
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# if such a process fails to find anything, there's no possible value
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proc valueRightOf(node: var BinaryTreeNode, path: BinaryTreeNodePath): Option[BinaryTreeNodePath] =
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# see valueLeftOf, but replace left<->right
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proc explodeAt(node: var BinaryTreeNode, path: BinaryTreeNodePath) =
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# TODO: implement exploding
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proc splitAt(node: var BinaryTreeNode, path: BinaryTreeNodePath) =
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# TODO: implement exploding
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proc p1(input: Lines): uint64 =
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var (bt, _) = input[0].parseBinaryTree()
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# TODO: iterate over the input, parsing into binary trees
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# fold over the binary trees, creating a new btree with each child btree as children
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# reduce that btree via explode/split rules
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# calculate magnitude
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let explodePath = bt.crawlFor((_, p) => p.len() > 4)
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let splitPath = bt.crawlFor((n, _) => n.kind == leaf and n.value >= 10)
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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, p1, (input, 4140'u64, 0'u64)
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