Xah Talk Show 2025-12-09 Ep721 Wolfram Language, Advent of Code 2025, Day 1, Problem 2
xah talk show ep721 2025-12 20d71
Video Summary (Generated by AI, Edited by Human.)
This video shows the process of solving Advent of Code 2025 Day 1 Problem 2 using Wolfram Language.
The creator explains the problem, which involves calculating the number of times a dial on a rotational lock points at zero, whether it stops there or passes by during rotation (3:23).
They attempt to model the lock's behavior using modular arithmetic to track the current position and the number of times zero is passed.
The creator writes a function to compute this, testing it with examples (36:27).
The video then goes through multiple debugging attempts, addressing edge cases like starting or ending at zero, and issues with sign conventions for left and right rotations (1:11:08).
Despite extensive debugging, they face continued challenges in getting the correct answer for the full input, leading to the session concluding with the problem still unsolved (3:00:28).
QuotientRemainder [c + n , 100]
Clear [xOperation]
xOperation::usage="xOperation[currentNumber, rotateN]
returns a list
{c,d}
c is the number of times it passed 0.
d is the new index number." ;
xOperation[currentNumber_, rotateN_] :=
QuotientRemainder [currentNumber + rotateN , 100]
xOperation[0,0]
xOperation[0,5]
xOperation[0,100]
xOperation[0,101]
xOperation[0,-100]
xOperation[5,0]
xOperation[5,-4]
xOperation[5,-5]
xOperation[5,-6]
xOperation[5,-99]
xOperation[5,-100]
xOperation[5,-600]
xOperation[5,5]
xOperation[5, 600]
Clear [doRotate]
doRotate::usage="
doRotate[{previousZeroCount, prevNumber}, rotateN]
returns a new {newZeroCount, prevNumber}.
where newZeroCount includes if current number is 0." ;
doRotate[{previousZeroCount_, prevNumber_}, rotateN_] :=
Block [{xquotient, xremainder},
{xquotient, xremainder} =
QuotientRemainder [prevNumber + rotateN , 100];
Print [ {previousZeroCount, prevNumber},{xquotient, xremainder} ];
{
previousZeroCount +
If [ xremainder == 0,
If [ prevNumber == 0, Max [Abs [xquotient] -1, 0] , Abs [xquotient] ],
Abs [xquotient]] ,
xremainder}
]
Fold [ doRotate , initState, xinput ]
FoldList [ doRotate , initState, xinput ]
Clear [doRotate]
doRotate::usage="
doRotate[{previousZeroCount, prevNumber}, rotateN]
returns a new {newZeroCount, prevNumber}.
where newZeroCount includes if current number is 0." ;
doRotate[{previousZeroCount_, prevNumber_}, rotateN_] :=
Block [{xquotient, xremainder},
{xquotient, xremainder} =
QuotientRemainder [prevNumber + rotateN , 100];
{
previousZeroCount +
If [ xremainder == 0,
If [ prevNumber == 0,
Max [Abs [xquotient] -1, 0] ,
Abs [xquotient]] ,
Abs [xquotient]] ,
xremainder}
]
Fold [ doRotate , initState, xinput ]
FoldList [ doRotate , initState, xinput ]
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