Rules: no spoilers.

The other rules are made up as we go along.

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  • @zogwarg
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    31 year ago
    spoiler

    Part 2 only, but Part 1 is very similar.

    #!/usr/bin/env jq -n -R -f
    [
      # For each line, get numbers eg: [ [1,2,3] ]
      inputs / " " | map(tonumber) | [ . ] |
    
      # Until latest row is all zeroes
      until (.[-1] | [ .[] == 0] | all;
       . += [
         # Add next row, where for element(i) = prev(i+1) - prev(i)
         [ .[-1][1:] , .[-1][0:-1] ] | transpose | map(.[0] - .[1])
        ]
      )
      # Get extrapolated previous element for first row
      |  [ .[][0] ] | reverse | reduce .[] as $i (0; $i - . )
    ]
    
    # Output sum of extapolations for all lines
    | add
    

    I’m pretty sure you could make this one line and unreadable ^^.

    • @swlabr
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      31 year ago

      Now this is content

    • @swlabr
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      31 year ago

      Here’s where I landed in dart

      no comments
      d9(bool s) {
        print(getLines().fold(0, (p, e) {
          int pre(List h, bool s) {
            return h.every((e) => e == 0)
                ? 0
                : (pre(List.generate(h.length - 1, (i) => h[i + 1] - h[i]), s)) *
                        (s ? -1 : 1) +
                    (s ? h.first : h.last);
          }
      
          return p + pre(stois(e), s);
        }));
      }