88 lines
2.6 KiB
Nim
88 lines
2.6 KiB
Nim
import std/[cmdline, sequtils, strformat, strutils, sugar, tables]
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type Position = tuple
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row: int
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col: int
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## Check if any of the grid cells adjacent to position (i, j) match condition cond.
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proc isAdjacentToCond(grid: seq[seq[char]], row, col: int, cond: (char) -> bool): Position =
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for i in @[row - 1, row, row + 1]:
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if i < 0 or i >= grid.len:
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continue
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for j in @[col - 1, col, col + 1]:
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if i == row and j == col:
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continue
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if j < 0 or j >= grid[i].len:
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continue
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var ch = grid[i][j]
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if cond(ch):
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return (i, j)
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return (-1, -1)
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var fn = if paramCount() > 0: paramStr(1) else: "input_03.txt"
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var result = 0
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# read input file as seq of lines
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var lines = readFile(fn).strip.splitLines
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# allocate 2-D seq to hold ros and colums of characters
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var grid = newSeqWith(lines.len, newSeq[char](lines[0].strip.len))
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# table to save positions of gears and parts connected to it
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var gears = initTable[Position, seq[int]]()
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# Parse input
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for i, line in lines:
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for j, ch in line.strip:
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grid[i][j] = ch
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#echo &"Rows: {grid.len}"
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#echo &"Cols: {grid[0].len}"
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# Go through grid and find positions of gears
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for i, row in grid:
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var
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isConnectedToGear = false
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gear: Position
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number = ""
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for j, ch in row:
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if ch.isDigit:
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number &= ch
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# Scan adjacent grid cells gor a gear ('*')
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var symbol = isAdjacentToCond(grid, i, j, (c) => c == '*')
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if symbol != (-1, -1):
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# It's a number adjacent to a gear!
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isConnectedToGear = true
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gear = symbol
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if not gears.hasKey(gear):
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# save gear position in table
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gears[gear] = newSeq[int]()
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else:
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if isConnectedToGear:
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# add part to gear position saved above
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# we can save an infinite amount of parts per gear
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# but we assume that at most two parts are connected to a gear
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gears[gear].add(number.parseInt)
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number = ""
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isConnectedToGear = false
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# account for numbers going until the end of the row
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if isConnectedToGear:
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# add part to gear position saved above
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gears[gear].add(number.parseInt)
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# Sum up gear ratios
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for pos, parts in gears:
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# Ignore gears conencted to only one part
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if parts.len > 1:
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result += parts[0] * parts[1]
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echo &"Result: {result}"
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case fn:
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of "input_03.txt":
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assert result == 86841457
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of "sample_input_03.txt":
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assert result == 467835
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