Add 2021-05 in Python

Signed-off-by: AKU <tom@tdpain.net>

challenges/2021/05-hydrothermalVenture/README.md

@@ -0,0 +1,23 @@
+# [Day 5: Hydrothermal Venture](https://adventofcode.com/2021/day/5)
+
+### Part one
+
+* Parse input and output a list of pairs of points.
+* Remove diagonal lines by filtering the list using the condition that `p1.x == p2.x or p1.y == p2.y`
+* Count overlapping points
+    * Create a dictionary that uses the point coordinate as a key and contains an integer `n` for each key
+    * Iterate over each line in the input, adding 1 to `n` for each coordinate in the line
+        * The coordinates were founid by computing the x and y deltas between the two points that made up the line
+        * The sign of the deltas determines the direction we step in
+        * We then step through each point in the line based on the step directions until the final point is encountered
+    * Iterate over all keys in the dictionary and count every point where `n > 1`
+
+### Part two
+
+The same as part one, but without the list filtering step.
+
+---
+
+Involved literal napkin maths.
+
+![napkin math](napkinmath.jpg)

challenges/2021/05-hydrothermalVenture/info.json

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+{
+    "inputFile": "input.txt",
+    "testCases": {
+        "one": [
+            {
+                "input": "0,9 -> 5,9\n8,0 -> 0,8\n9,4 -> 3,4\n2,2 -> 2,1\n7,0 -> 7,4\n6,4 -> 2,0\n0,9 -> 2,9\n3,4 -> 1,4\n0,0 -> 8,8\n5,5 -> 8,2\n",
+                "expected": "5"
+            }
+        ],
+        "two": [
+            {
+                "input": "0,9 -> 5,9\n8,0 -> 0,8\n9,4 -> 3,4\n2,2 -> 2,1\n7,0 -> 7,4\n6,4 -> 2,0\n0,9 -> 2,9\n3,4 -> 1,4\n0,0 -> 8,8\n5,5 -> 8,2\n",
+                "expected": "12"
+            }
+        ]
+    }
+}

challenges/2021/05-hydrothermalVenture/py/__init__.py

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+import time
+from typing import Tuple, List, Generator
+from aocpy import BaseChallenge
+from dataclasses import dataclass
+
+
+@dataclass
+class Point:
+    x: int
+    y: int
+
+    def __init__(self, p: str):
+        x, y = p.split(",")
+        self.x = int(x)
+        self.y = int(y)
+
+    def as_tuple(self) -> Tuple[int, int]:
+        return (self.x, self.y)
+
+
+Line = Tuple[Point, Point]
+
+
+def parse(instr: str) -> List[Line]:
+    o = []
+    for line in instr.strip().splitlines():
+        p1, p2 = line.split(" -> ")
+        o.append((Point(p1), Point(p2)))
+    return o
+
+
+def remove_diagonal_lines(lines: List[Line]):
+    return list(
+        filter(
+            lambda line: line[0].x == line[1].x or line[0].y == line[1].y,
+            lines,
+        )
+    )
+
+
+def iterate_points(line: Line) -> Generator[Point, None, None]:
+    p1, p2 = line
+    delta_x = p2.x - p1.x
+    delta_y = p2.y - p1.y
+
+    x_step = 0
+    y_step = 0
+
+    if delta_x > 0:
+        x_step = 1
+    elif delta_x < 0:
+        x_step = -1
+
+    if delta_y > 0:
+        y_step = 1
+    elif delta_y < 0:
+        y_step = -1
+
+    last_point = p1
+    yield p1
+    while last_point != p2:
+        np = Point(f"{last_point.x+x_step},{last_point.y+y_step}")
+        yield np
+        last_point = np
+
+
+def count_overlapping_points(lines: List[Line]) -> int:
+    areas = {}
+    for line in lines:
+        for point in iterate_points(line):
+            t = point.as_tuple()
+            areas[t] = areas.get(t, 0) + 1
+
+    number_overlaps = 0
+    for point in areas:
+        if areas[point] > 1:
+            number_overlaps += 1
+
+    return number_overlaps
+
+
+class Challenge(BaseChallenge):
+    @staticmethod
+    def one(instr: str) -> int:
+        lines = parse(instr)
+        lines = remove_diagonal_lines(lines)
+        return count_overlapping_points(lines)
+
+    @staticmethod
+    def two(instr: str) -> int:
+        lines = parse(instr)
+        return count_overlapping_points(lines)

challenges/2021/README.md

@@ -14,5 +14,6 @@ Solutions to the [2021 Advent of Code](https://adventofcode.com/2021).
 | 02 - Dive!                          | Complete           | [Python](02-dive/py), [Go](02-dive/go)                                       | Have this set of instructions and do something sensible with it. |
 | 03 - Binary Diagnostic              | Complete           | [Python](03-binaryDiagnostic/py), [Nim](03-binaryDiagnostic/nim)             | Bit twiddling aplenty!                                           |
 | 04 - Giant Squid                    | Complete           | [Python](04-giantSquid/py)                                                   | B-I-N-G-O, B-I-N-G-O, B-I-N-G-O and Bingo was his name-o!        |
+| 05 - Hydrothermal Venture           | Complete           | [Python](05-hydrothermalVenture/py)                                          | Pointy.                                                          |
 
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