Advent of Code 2018 day 1 part 2: find the first aggregated number that occures twice
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I am using the coding puzzels of https://adventofcode.com for improving my F# skills.
Problem:
Day 1 Part 2:
Starting with frequency 0, a list of numbers should be added successive generating new frequencies. Searched is the first frequency which occurs twice. If the end of the list has been reached without success; the list should be processed again.
Example Input: [+1, -2, +3, +1]
- Current frequency 0, change of +1; resulting frequency 1.
- Current frequency 1, change of -2; resulting frequency -1.
C* urrent frequency -1, change of +3; resulting frequency 2.
- Current frequency 2, change of +1; resulting frequency 3.
(At this point, we continue from the start of the list.)
- Current frequency 3, change of +1; resulting frequency 4.
- Current frequency 4, change of -2; resulting frequency 2, which has already been seen.
In this example, the first frequency reached twice is 2.
Solution
let input = [1;-2;3;1]
type State =
| FinalState of int
| IntermediateState of int * int Set
type State with
static member Zero = IntermediateState(0, Set.empty.Add(0))
let foldIntermediateState (freqHistory: int Set, freq : int) : State =
let isFinal = freqHistory |> Set.contains freq
if isFinal then
FinalState (freq)
else
IntermediateState (freq, freqHistory.Add(freq))
let foldState state value =
match state with
| FinalState _ -> state
| IntermediateState (lastFreq, freqHistory) -> foldIntermediateState (freqHistory, lastFreq + value)
let rec processListRec state lst =
let result = lst |> Seq.fold foldState state
match result with
| FinalState result -> printfn "The result is: %i" result
| IntermediateState _ -> lst |> processListRec result
input |> Seq.map int |> processListRec State.Zero
Questions
In fact, I am proud to have found a solution without mutable states that looks (at least for me) functional! :D. So any feeback that helps improving the solution or even alternative function approches for solving that problem are welcome :).
programming-challenge functional-programming f#
add a comment |
up vote
2
down vote
favorite
I am using the coding puzzels of https://adventofcode.com for improving my F# skills.
Problem:
Day 1 Part 2:
Starting with frequency 0, a list of numbers should be added successive generating new frequencies. Searched is the first frequency which occurs twice. If the end of the list has been reached without success; the list should be processed again.
Example Input: [+1, -2, +3, +1]
- Current frequency 0, change of +1; resulting frequency 1.
- Current frequency 1, change of -2; resulting frequency -1.
C* urrent frequency -1, change of +3; resulting frequency 2.
- Current frequency 2, change of +1; resulting frequency 3.
(At this point, we continue from the start of the list.)
- Current frequency 3, change of +1; resulting frequency 4.
- Current frequency 4, change of -2; resulting frequency 2, which has already been seen.
In this example, the first frequency reached twice is 2.
Solution
let input = [1;-2;3;1]
type State =
| FinalState of int
| IntermediateState of int * int Set
type State with
static member Zero = IntermediateState(0, Set.empty.Add(0))
let foldIntermediateState (freqHistory: int Set, freq : int) : State =
let isFinal = freqHistory |> Set.contains freq
if isFinal then
FinalState (freq)
else
IntermediateState (freq, freqHistory.Add(freq))
let foldState state value =
match state with
| FinalState _ -> state
| IntermediateState (lastFreq, freqHistory) -> foldIntermediateState (freqHistory, lastFreq + value)
let rec processListRec state lst =
let result = lst |> Seq.fold foldState state
match result with
| FinalState result -> printfn "The result is: %i" result
| IntermediateState _ -> lst |> processListRec result
input |> Seq.map int |> processListRec State.Zero
Questions
In fact, I am proud to have found a solution without mutable states that looks (at least for me) functional! :D. So any feeback that helps improving the solution or even alternative function approches for solving that problem are welcome :).
programming-challenge functional-programming f#
add a comment |
up vote
2
down vote
favorite
up vote
2
down vote
favorite
I am using the coding puzzels of https://adventofcode.com for improving my F# skills.
Problem:
Day 1 Part 2:
Starting with frequency 0, a list of numbers should be added successive generating new frequencies. Searched is the first frequency which occurs twice. If the end of the list has been reached without success; the list should be processed again.
Example Input: [+1, -2, +3, +1]
- Current frequency 0, change of +1; resulting frequency 1.
- Current frequency 1, change of -2; resulting frequency -1.
C* urrent frequency -1, change of +3; resulting frequency 2.
- Current frequency 2, change of +1; resulting frequency 3.
(At this point, we continue from the start of the list.)
- Current frequency 3, change of +1; resulting frequency 4.
- Current frequency 4, change of -2; resulting frequency 2, which has already been seen.
In this example, the first frequency reached twice is 2.
Solution
let input = [1;-2;3;1]
type State =
| FinalState of int
| IntermediateState of int * int Set
type State with
static member Zero = IntermediateState(0, Set.empty.Add(0))
let foldIntermediateState (freqHistory: int Set, freq : int) : State =
let isFinal = freqHistory |> Set.contains freq
if isFinal then
FinalState (freq)
else
IntermediateState (freq, freqHistory.Add(freq))
let foldState state value =
match state with
| FinalState _ -> state
| IntermediateState (lastFreq, freqHistory) -> foldIntermediateState (freqHistory, lastFreq + value)
let rec processListRec state lst =
let result = lst |> Seq.fold foldState state
match result with
| FinalState result -> printfn "The result is: %i" result
| IntermediateState _ -> lst |> processListRec result
input |> Seq.map int |> processListRec State.Zero
Questions
In fact, I am proud to have found a solution without mutable states that looks (at least for me) functional! :D. So any feeback that helps improving the solution or even alternative function approches for solving that problem are welcome :).
programming-challenge functional-programming f#
I am using the coding puzzels of https://adventofcode.com for improving my F# skills.
Problem:
Day 1 Part 2:
Starting with frequency 0, a list of numbers should be added successive generating new frequencies. Searched is the first frequency which occurs twice. If the end of the list has been reached without success; the list should be processed again.
Example Input: [+1, -2, +3, +1]
- Current frequency 0, change of +1; resulting frequency 1.
- Current frequency 1, change of -2; resulting frequency -1.
C* urrent frequency -1, change of +3; resulting frequency 2.
- Current frequency 2, change of +1; resulting frequency 3.
(At this point, we continue from the start of the list.)
- Current frequency 3, change of +1; resulting frequency 4.
- Current frequency 4, change of -2; resulting frequency 2, which has already been seen.
In this example, the first frequency reached twice is 2.
Solution
let input = [1;-2;3;1]
type State =
| FinalState of int
| IntermediateState of int * int Set
type State with
static member Zero = IntermediateState(0, Set.empty.Add(0))
let foldIntermediateState (freqHistory: int Set, freq : int) : State =
let isFinal = freqHistory |> Set.contains freq
if isFinal then
FinalState (freq)
else
IntermediateState (freq, freqHistory.Add(freq))
let foldState state value =
match state with
| FinalState _ -> state
| IntermediateState (lastFreq, freqHistory) -> foldIntermediateState (freqHistory, lastFreq + value)
let rec processListRec state lst =
let result = lst |> Seq.fold foldState state
match result with
| FinalState result -> printfn "The result is: %i" result
| IntermediateState _ -> lst |> processListRec result
input |> Seq.map int |> processListRec State.Zero
Questions
In fact, I am proud to have found a solution without mutable states that looks (at least for me) functional! :D. So any feeback that helps improving the solution or even alternative function approches for solving that problem are welcome :).
programming-challenge functional-programming f#
programming-challenge functional-programming f#
asked yesterday
JanDotNet
6,6061239
6,6061239
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add a comment |
1 Answer
1
active
oldest
votes
up vote
1
down vote
Caveat : I don't know F#.
I liked your solution, the use of algebraic data types, pattern matching and use of list processing via fold and higher order functions are good.
However I'm trying to apply a functional style in python (which I'm learning) and I think there is a way to do this that use simple list data structures, with (list) comprehension or the equivalent
Here is my attempt in python to present an alternative approach
import functools
import itertools
fchanges =
with open('frequency_input') as f:
for line in f:
fchanges.append(int(line))
frequencies = [sum(fchanges[:index]) for index in range(1, len(fchanges)+1)]
skew = frequencies[-1]
print('Skew is ' + str(skew))
accumulator = itertools.accumulate(itertools.cycle(fchanges))
prefix = itertools.takewhile(lambda x: (x + skew) not in frequencies, accumulator)
# takewhile consumes the value I'm looking for to check the predicate, hence this hack
# don't need the list, memory optimization - just need the length
plen = functools.reduce(lambda x, y: x+1, prefix, 0)
accumulator = itertools.accumulate(itertools.cycle(fchanges))
print('found first repetition ' + str(next(itertools.islice(accumulator, plen, None)) + skew))
Happy to receive feedback on my attempt too for any observers.
add a comment |
1 Answer
1
active
oldest
votes
1 Answer
1
active
oldest
votes
active
oldest
votes
active
oldest
votes
up vote
1
down vote
Caveat : I don't know F#.
I liked your solution, the use of algebraic data types, pattern matching and use of list processing via fold and higher order functions are good.
However I'm trying to apply a functional style in python (which I'm learning) and I think there is a way to do this that use simple list data structures, with (list) comprehension or the equivalent
Here is my attempt in python to present an alternative approach
import functools
import itertools
fchanges =
with open('frequency_input') as f:
for line in f:
fchanges.append(int(line))
frequencies = [sum(fchanges[:index]) for index in range(1, len(fchanges)+1)]
skew = frequencies[-1]
print('Skew is ' + str(skew))
accumulator = itertools.accumulate(itertools.cycle(fchanges))
prefix = itertools.takewhile(lambda x: (x + skew) not in frequencies, accumulator)
# takewhile consumes the value I'm looking for to check the predicate, hence this hack
# don't need the list, memory optimization - just need the length
plen = functools.reduce(lambda x, y: x+1, prefix, 0)
accumulator = itertools.accumulate(itertools.cycle(fchanges))
print('found first repetition ' + str(next(itertools.islice(accumulator, plen, None)) + skew))
Happy to receive feedback on my attempt too for any observers.
add a comment |
up vote
1
down vote
Caveat : I don't know F#.
I liked your solution, the use of algebraic data types, pattern matching and use of list processing via fold and higher order functions are good.
However I'm trying to apply a functional style in python (which I'm learning) and I think there is a way to do this that use simple list data structures, with (list) comprehension or the equivalent
Here is my attempt in python to present an alternative approach
import functools
import itertools
fchanges =
with open('frequency_input') as f:
for line in f:
fchanges.append(int(line))
frequencies = [sum(fchanges[:index]) for index in range(1, len(fchanges)+1)]
skew = frequencies[-1]
print('Skew is ' + str(skew))
accumulator = itertools.accumulate(itertools.cycle(fchanges))
prefix = itertools.takewhile(lambda x: (x + skew) not in frequencies, accumulator)
# takewhile consumes the value I'm looking for to check the predicate, hence this hack
# don't need the list, memory optimization - just need the length
plen = functools.reduce(lambda x, y: x+1, prefix, 0)
accumulator = itertools.accumulate(itertools.cycle(fchanges))
print('found first repetition ' + str(next(itertools.islice(accumulator, plen, None)) + skew))
Happy to receive feedback on my attempt too for any observers.
add a comment |
up vote
1
down vote
up vote
1
down vote
Caveat : I don't know F#.
I liked your solution, the use of algebraic data types, pattern matching and use of list processing via fold and higher order functions are good.
However I'm trying to apply a functional style in python (which I'm learning) and I think there is a way to do this that use simple list data structures, with (list) comprehension or the equivalent
Here is my attempt in python to present an alternative approach
import functools
import itertools
fchanges =
with open('frequency_input') as f:
for line in f:
fchanges.append(int(line))
frequencies = [sum(fchanges[:index]) for index in range(1, len(fchanges)+1)]
skew = frequencies[-1]
print('Skew is ' + str(skew))
accumulator = itertools.accumulate(itertools.cycle(fchanges))
prefix = itertools.takewhile(lambda x: (x + skew) not in frequencies, accumulator)
# takewhile consumes the value I'm looking for to check the predicate, hence this hack
# don't need the list, memory optimization - just need the length
plen = functools.reduce(lambda x, y: x+1, prefix, 0)
accumulator = itertools.accumulate(itertools.cycle(fchanges))
print('found first repetition ' + str(next(itertools.islice(accumulator, plen, None)) + skew))
Happy to receive feedback on my attempt too for any observers.
Caveat : I don't know F#.
I liked your solution, the use of algebraic data types, pattern matching and use of list processing via fold and higher order functions are good.
However I'm trying to apply a functional style in python (which I'm learning) and I think there is a way to do this that use simple list data structures, with (list) comprehension or the equivalent
Here is my attempt in python to present an alternative approach
import functools
import itertools
fchanges =
with open('frequency_input') as f:
for line in f:
fchanges.append(int(line))
frequencies = [sum(fchanges[:index]) for index in range(1, len(fchanges)+1)]
skew = frequencies[-1]
print('Skew is ' + str(skew))
accumulator = itertools.accumulate(itertools.cycle(fchanges))
prefix = itertools.takewhile(lambda x: (x + skew) not in frequencies, accumulator)
# takewhile consumes the value I'm looking for to check the predicate, hence this hack
# don't need the list, memory optimization - just need the length
plen = functools.reduce(lambda x, y: x+1, prefix, 0)
accumulator = itertools.accumulate(itertools.cycle(fchanges))
print('found first repetition ' + str(next(itertools.islice(accumulator, plen, None)) + skew))
Happy to receive feedback on my attempt too for any observers.
answered yesterday
Bhaskar
27112
27112
add a comment |
add a comment |
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