Add 2015 Day 9

Author: lukasgabriel

2015/9/2015_09.md

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+# --- Day 9: All in a Single Night ---
+
+Every year, Santa manages to deliver all of his presents in a single night.
+
+This year, however, he has some new locations to visit; his elves have provided him the distances between every pair of locations. He can start and end at any two (different) locations he wants, but he must visit each location exactly once. What is the shortest distance he can travel to achieve this?
+
+For example, given the following distances:
+
+```text
+London to Dublin = 464
+London to Belfast = 518
+Dublin to Belfast = 141
+```
+
+The possible routes are therefore:
+
+```text
+Dublin -> London -> Belfast = 982
+London -> Dublin -> Belfast = 605
+London -> Belfast -> Dublin = 659
+Dublin -> Belfast -> London = 659
+Belfast -> Dublin -> London = 605
+Belfast -> London -> Dublin = 982
+```
+
+The shortest of these is `London -> Dublin -> Belfast = 605`, and so the answer is 605 in this example.
+
+What is the distance of the shortest route?

2015/9/2015_09.txt

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+AlphaCentauri to Snowdin = 66
+AlphaCentauri to Tambi = 28
+AlphaCentauri to Faerun = 60
+AlphaCentauri to Norrath = 34
+AlphaCentauri to Straylight = 34
+AlphaCentauri to Tristram = 3
+AlphaCentauri to Arbre = 108
+Snowdin to Tambi = 22
+Snowdin to Faerun = 12
+Snowdin to Norrath = 91
+Snowdin to Straylight = 121
+Snowdin to Tristram = 111
+Snowdin to Arbre = 71
+Tambi to Faerun = 39
+Tambi to Norrath = 113
+Tambi to Straylight = 130
+Tambi to Tristram = 35
+Tambi to Arbre = 40
+Faerun to Norrath = 63
+Faerun to Straylight = 21
+Faerun to Tristram = 57
+Faerun to Arbre = 83
+Norrath to Straylight = 9
+Norrath to Tristram = 50
+Norrath to Arbre = 60
+Straylight to Tristram = 27
+Straylight to Arbre = 81
+Tristram to Arbre = 90

2015/9/2015_09_01.py

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+# Advent of Code 2015, Day 9: All in a Single Night. Part 1
+# https://adventofcode.com/2015/day/9
+
+import re
+import networkx as nx
+
+
+def main():
+    solution = 0
+    pairings = []
+
+    # Get pairings and distances from file
+    for line in open("./2015/9/2015_09.txt", "r", encoding="utf-8"):
+        pairings.append(re.split(r" to | = ", line.strip()))
+
+    # Build graph
+    G = nx.Graph()
+    for pairing in pairings:
+        G.add_edge(pairing[0], pairing[1], weight=int(pairing[2]))
+
+    # Find shortest path visiting every node exactly once by brute force
+    
+       
+    return f"The shortest possible distance is {solution}"
+
+
+if __name__ == "__main__":
+    print(main())