From 81079f201913173f1adc8db8df8f393199d25ed8 Mon Sep 17 00:00:00 2001
From: Dan Katzuv <dan.dan.kafe@gmail.com>
Date: Wed, 21 Dec 2022 17:16:45 +0200
Subject: [PATCH 01/16] Create solution file for part 1

---
 puzzles/solutions/2022/d09/p1.py | 12 ++++++++++++
 1 file changed, 12 insertions(+)
 create mode 100644 puzzles/solutions/2022/d09/p1.py

diff --git a/puzzles/solutions/2022/d09/p1.py b/puzzles/solutions/2022/d09/p1.py
new file mode 100644
index 00000000..c3bbf496
--- /dev/null
+++ b/puzzles/solutions/2022/d09/p1.py
@@ -0,0 +1,12 @@
+import sys
+
+
+def get_answer(input_text: str):
+    raise NotImplementedError
+
+
+if __name__ == "__main__":
+    try:
+        print(get_answer(sys.argv[1]))
+    except IndexError:
+        pass  # Don't crash if no input was passed through command line arguments.

From 91572fa2db1d48e3b6810feeeba1a7f4bde48e30 Mon Sep 17 00:00:00 2001
From: Dan Katzuv <dan.dan.kafe@gmail.com>
Date: Wed, 21 Dec 2022 17:22:19 +0200
Subject: [PATCH 02/16] Add constants module

---
 puzzles/solutions/2022/d09/consts.py | 0
 1 file changed, 0 insertions(+), 0 deletions(-)
 create mode 100644 puzzles/solutions/2022/d09/consts.py

diff --git a/puzzles/solutions/2022/d09/consts.py b/puzzles/solutions/2022/d09/consts.py
new file mode 100644
index 00000000..e69de29b

From 3fea21d1df905d42c451968d7e0e0b4fa66146ef Mon Sep 17 00:00:00 2001
From: Dan Katzuv <dan.dan.kafe@gmail.com>
Date: Wed, 21 Dec 2022 17:27:03 +0200
Subject: [PATCH 03/16] Add mapping between direction to step

---
 puzzles/solutions/2022/d09/consts.py | 1 +
 1 file changed, 1 insertion(+)

diff --git a/puzzles/solutions/2022/d09/consts.py b/puzzles/solutions/2022/d09/consts.py
index e69de29b..5a7e58f5 100644
--- a/puzzles/solutions/2022/d09/consts.py
+++ b/puzzles/solutions/2022/d09/consts.py
@@ -0,0 +1 @@
+DIRECTION_TO_STEP = {"R": (1, 0), "U": (0, 1), "L": (-1, 0), "D": (0, -1)}

From c6e7c1e1059e2eafe1e60108cfdab75aa113082d Mon Sep 17 00:00:00 2001
From: Dan Katzuv <dan.dan.kafe@gmail.com>
Date: Wed, 21 Dec 2022 17:21:15 +0200
Subject: [PATCH 04/16] Add function that creates a sequence of steps from the
 input

---
 puzzles/solutions/2022/d09/p1.py | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/puzzles/solutions/2022/d09/p1.py b/puzzles/solutions/2022/d09/p1.py
index c3bbf496..4478736b 100644
--- a/puzzles/solutions/2022/d09/p1.py
+++ b/puzzles/solutions/2022/d09/p1.py
@@ -1,4 +1,21 @@
 import sys
+from typing import Iterator
+
+import consts
+
+
+def get_steps(input_text: str) -> Iterator[tuple[int, int]]:
+    """
+    :param input_text: puzzle input
+    :return: sequence of steps, one by one
+    """
+    steps = []
+    for step_count in input_text.splitlines():
+        direction, count = step_count.split()
+        step = consts.DIRECTION_TO_STEP[direction]
+        count = int(count)
+        yield from count * [step]
+    return tuple(steps)
 
 
 def get_answer(input_text: str):

From 8dec2f08ec87b3aff96372850c55aa631b4f8c55 Mon Sep 17 00:00:00 2001
From: Dan Katzuv <dan.dan.kafe@gmail.com>
Date: Wed, 21 Dec 2022 17:28:54 +0200
Subject: [PATCH 05/16] Create module for `Knot` class

---
 puzzles/solutions/2022/d09/knot.py | 0
 1 file changed, 0 insertions(+), 0 deletions(-)
 create mode 100644 puzzles/solutions/2022/d09/knot.py

diff --git a/puzzles/solutions/2022/d09/knot.py b/puzzles/solutions/2022/d09/knot.py
new file mode 100644
index 00000000..e69de29b

From 334b0791ecf9c0c17b0297056fc6b5c10ba35392 Mon Sep 17 00:00:00 2001
From: Dan Katzuv <dan.dan.kafe@gmail.com>
Date: Wed, 21 Dec 2022 17:29:30 +0200
Subject: [PATCH 06/16] Create `Knot` class

---
 puzzles/solutions/2022/d09/knot.py | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/puzzles/solutions/2022/d09/knot.py b/puzzles/solutions/2022/d09/knot.py
index e69de29b..599e4739 100644
--- a/puzzles/solutions/2022/d09/knot.py
+++ b/puzzles/solutions/2022/d09/knot.py
@@ -0,0 +1,6 @@
+import dataclasses
+
+
+@dataclasses.dataclass
+class Knot:
+    """A knot on a rope which can move."""

From 67e9ab821cb461c64935a4bd5b5f9748a6a7b3c7 Mon Sep 17 00:00:00 2001
From: Dan Katzuv <dan.dan.kafe@gmail.com>
Date: Wed, 21 Dec 2022 17:30:02 +0200
Subject: [PATCH 07/16] Add "column" field to `Step` class

---
 puzzles/solutions/2022/d09/knot.py | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/puzzles/solutions/2022/d09/knot.py b/puzzles/solutions/2022/d09/knot.py
index 599e4739..3f0fdf1e 100644
--- a/puzzles/solutions/2022/d09/knot.py
+++ b/puzzles/solutions/2022/d09/knot.py
@@ -4,3 +4,6 @@
 @dataclasses.dataclass
 class Knot:
     """A knot on a rope which can move."""
+
+    row: int
+    column: int

From e20b6844fd0dea14b71b46fc8aff51974a500dd3 Mon Sep 17 00:00:00 2001
From: Dan Katzuv <dan.dan.kafe@gmail.com>
Date: Wed, 21 Dec 2022 17:32:10 +0200
Subject: [PATCH 08/16] Add method that moves a knot

---
 puzzles/solutions/2022/d09/knot.py | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/puzzles/solutions/2022/d09/knot.py b/puzzles/solutions/2022/d09/knot.py
index 3f0fdf1e..3a315c5f 100644
--- a/puzzles/solutions/2022/d09/knot.py
+++ b/puzzles/solutions/2022/d09/knot.py
@@ -7,3 +7,12 @@ class Knot:
 
     row: int
     column: int
+
+    def move(self, step: tuple[int, int]) -> None:
+        """
+        Move the knot by the given step.
+        :param step: pair of (row, column) movement
+        """
+        x, y = step
+        self.row += x
+        self.column += y

From 840d54066187e56fb274bbfcc57a4cb6a8e9bf2b Mon Sep 17 00:00:00 2001
From: Dan Katzuv <dan.dan.kafe@gmail.com>
Date: Sat, 24 Dec 2022 15:49:07 +0200
Subject: [PATCH 09/16] Add constant for distance between knots to be
 "adjacent" to each other

---
 puzzles/solutions/2022/d09/consts.py | 1 +
 1 file changed, 1 insertion(+)

diff --git a/puzzles/solutions/2022/d09/consts.py b/puzzles/solutions/2022/d09/consts.py
index 5a7e58f5..dbd8a2f7 100644
--- a/puzzles/solutions/2022/d09/consts.py
+++ b/puzzles/solutions/2022/d09/consts.py
@@ -1 +1,2 @@
 DIRECTION_TO_STEP = {"R": (1, 0), "U": (0, 1), "L": (-1, 0), "D": (0, -1)}
+ADJACENT_DISTANCE = 1

From cf72e9242aa19d3700f04a7f9abbb26c2f5ab568 Mon Sep 17 00:00:00 2001
From: Dan Katzuv <dan.dan.kafe@gmail.com>
Date: Wed, 21 Dec 2022 17:39:03 +0200
Subject: [PATCH 10/16] Add constant for distance between knots to be "far"
 from each other

---
 puzzles/solutions/2022/d09/consts.py | 1 +
 1 file changed, 1 insertion(+)

diff --git a/puzzles/solutions/2022/d09/consts.py b/puzzles/solutions/2022/d09/consts.py
index dbd8a2f7..7492e5b5 100644
--- a/puzzles/solutions/2022/d09/consts.py
+++ b/puzzles/solutions/2022/d09/consts.py
@@ -1,2 +1,3 @@
 DIRECTION_TO_STEP = {"R": (1, 0), "U": (0, 1), "L": (-1, 0), "D": (0, -1)}
 ADJACENT_DISTANCE = 1
+FAR_DISTANCE = 2

From 01f7938e2dfdd313ecf9149b76dcb4d1e997cff3 Mon Sep 17 00:00:00 2001
From: Dan Katzuv <dan.dan.kafe@gmail.com>
Date: Wed, 21 Dec 2022 17:40:45 +0200
Subject: [PATCH 11/16] Add method that returns whether a knot and another knot
 are touching

---
 puzzles/solutions/2022/d09/knot.py | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/puzzles/solutions/2022/d09/knot.py b/puzzles/solutions/2022/d09/knot.py
index 3a315c5f..51696fc9 100644
--- a/puzzles/solutions/2022/d09/knot.py
+++ b/puzzles/solutions/2022/d09/knot.py
@@ -1,5 +1,9 @@
 import dataclasses
 
+from typing import Self
+
+import consts
+
 
 @dataclasses.dataclass
 class Knot:
@@ -16,3 +20,13 @@ def move(self, step: tuple[int, int]) -> None:
         x, y = step
         self.row += x
         self.column += y
+
+    def is_touching(self, other: Self) -> bool:
+        """
+        :param other: other knot
+        :return: whether this knot and the other knot are touching
+        """
+        return (
+            abs(self.row - other.row) < consts.FAR_DISTANCE
+            and abs(self.column - other.column) < consts.FAR_DISTANCE
+        )

From 697a6b982e3b9f00790b1c064a864cbab68bbe76 Mon Sep 17 00:00:00 2001
From: Dan Katzuv <dan.dan.kafe@gmail.com>
Date: Fri, 23 Dec 2022 16:17:52 +0200
Subject: [PATCH 12/16] Add method that moves a knot to be touching another
 knot

---
 puzzles/solutions/2022/d09/knot.py | 25 +++++++++++++++++++++++++
 1 file changed, 25 insertions(+)

diff --git a/puzzles/solutions/2022/d09/knot.py b/puzzles/solutions/2022/d09/knot.py
index 51696fc9..b2059782 100644
--- a/puzzles/solutions/2022/d09/knot.py
+++ b/puzzles/solutions/2022/d09/knot.py
@@ -1,4 +1,5 @@
 import dataclasses
+import math
 
 from typing import Self
 
@@ -30,3 +31,27 @@ def is_touching(self, other: Self) -> bool:
             abs(self.row - other.row) < consts.FAR_DISTANCE
             and abs(self.column - other.column) < consts.FAR_DISTANCE
         )
+
+    def move_to_other(self, other: Self) -> None:
+        """
+        Move this knot, so it will be touching the other knot.
+        :param other: other knot to move towards.
+        """
+        if self.is_touching(other):
+            return
+
+        row_distance = self.row - other.row
+        column_distance = self.column - other.column
+
+        # If the distance is "far", we want to move the knot, so it will be on the same row/column, but not overlapping,
+        #   so the distance to move should be 1.
+        # If the distance is "adjacent", it means we want to move diagonally (remember -- the knots are not touching,
+        #   otherwise, we would return immediately at the beginning of this method), so the distance to move
+        #   stays 1, too.
+        # If the distance is 0, no movement should occur, the condition is falsy, so the distance to move stays 0.
+        if abs(row_distance) == consts.FAR_DISTANCE:
+            row_distance = math.copysign(consts.ADJACENT_DISTANCE, row_distance)
+        if abs(column_distance) == consts.FAR_DISTANCE:
+            column_distance = math.copysign(consts.ADJACENT_DISTANCE, column_distance)
+
+        self.move((-int(row_distance), -int(column_distance)))

From a6d6e00bdd9c4406785477b99e94b66b64298040 Mon Sep 17 00:00:00 2001
From: Dan Katzuv <dan.dan.kafe@gmail.com>
Date: Sat, 24 Dec 2022 20:11:13 +0200
Subject: [PATCH 13/16] Add function that simulates a rope movement with a
 given amount of knots

---
 puzzles/solutions/2022/d09/p1.py | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)

diff --git a/puzzles/solutions/2022/d09/p1.py b/puzzles/solutions/2022/d09/p1.py
index 4478736b..04ab0edd 100644
--- a/puzzles/solutions/2022/d09/p1.py
+++ b/puzzles/solutions/2022/d09/p1.py
@@ -18,6 +18,27 @@ def get_steps(input_text: str) -> Iterator[tuple[int, int]]:
     return tuple(steps)
 
 
+def get_visited_positions_amount(
+    steps: Iterator[tuple[int, int]], knots_amount: int
+) -> int:
+    """
+    :param steps: sequence of steps, one by one
+    :param knots_amount: amount of knots in the rope
+    :return: number of positions the tail of the rope visits at least once
+    """
+    knots = [Knot(0, 0) for _ in range(knots_amount)]
+    head = knots[0]
+    tail = knots[-1]
+    visited_positions = set()
+    for step in steps:
+        head.move(step)
+        for index in range(1, knots_amount):
+            # Move each knot according to the knot it follows.
+            knots[index].move_to_other(knots[index - 1])
+        visited_positions.add((tail.row, tail.column))
+    return len(visited_positions)
+
+
 def get_answer(input_text: str):
     raise NotImplementedError
 

From 2d308a68e52dfef2f16511ba036640d0e5bed2fb Mon Sep 17 00:00:00 2001
From: Dan Katzuv <dan.dan.kafe@gmail.com>
Date: Sat, 24 Dec 2022 20:12:31 +0200
Subject: [PATCH 14/16] Add a function that returns number of positions tail of
 the rope visits

This is for a rope with two knots.
---
 puzzles/solutions/2022/d09/p1.py | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/puzzles/solutions/2022/d09/p1.py b/puzzles/solutions/2022/d09/p1.py
index 04ab0edd..206fec78 100644
--- a/puzzles/solutions/2022/d09/p1.py
+++ b/puzzles/solutions/2022/d09/p1.py
@@ -1,6 +1,7 @@
 import sys
 from typing import Iterator
 
+from knot import Knot
 import consts
 
 
@@ -40,7 +41,9 @@ def get_visited_positions_amount(
 
 
 def get_answer(input_text: str):
-    raise NotImplementedError
+    """Return the number of positions the tail of the rope visits at least once, when the rope has total 2 knots."""
+    steps = get_steps(input_text)
+    return get_visited_positions_amount(steps, 2)
 
 
 if __name__ == "__main__":

From 29c2e56d187cff986bcb9c6546b10d48df38374d Mon Sep 17 00:00:00 2001
From: Dan Katzuv <dan.dan.kafe@gmail.com>
Date: Sat, 24 Dec 2022 20:13:14 +0200
Subject: [PATCH 15/16] Create solution file for part 2

---
 puzzles/solutions/2022/d09/p2.py | 12 ++++++++++++
 1 file changed, 12 insertions(+)
 create mode 100644 puzzles/solutions/2022/d09/p2.py

diff --git a/puzzles/solutions/2022/d09/p2.py b/puzzles/solutions/2022/d09/p2.py
new file mode 100644
index 00000000..c3bbf496
--- /dev/null
+++ b/puzzles/solutions/2022/d09/p2.py
@@ -0,0 +1,12 @@
+import sys
+
+
+def get_answer(input_text: str):
+    raise NotImplementedError
+
+
+if __name__ == "__main__":
+    try:
+        print(get_answer(sys.argv[1]))
+    except IndexError:
+        pass  # Don't crash if no input was passed through command line arguments.

From 66aaa28f5b172b1a8f9d8afa95aeeaac4999afa2 Mon Sep 17 00:00:00 2001
From: Dan Katzuv <dan.dan.kafe@gmail.com>
Date: Sat, 24 Dec 2022 20:14:38 +0200
Subject: [PATCH 16/16] Add a function that returns number of positions tail of
 the rope visits

This is for a rope with ten knots.
---
 puzzles/solutions/2022/d09/p2.py | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/puzzles/solutions/2022/d09/p2.py b/puzzles/solutions/2022/d09/p2.py
index c3bbf496..e34bc55d 100644
--- a/puzzles/solutions/2022/d09/p2.py
+++ b/puzzles/solutions/2022/d09/p2.py
@@ -1,8 +1,12 @@
 import sys
 
+import p1
+
 
 def get_answer(input_text: str):
-    raise NotImplementedError
+    """Return the number of positions the tail of the rope visits at least once, when the rope has total 10 knots."""
+    steps = p1.get_steps(input_text)
+    return p1.get_visited_positions_amount(steps, 10)
 
 
 if __name__ == "__main__":