From d32f63fb5cbe365a99384a11e4bfecd6b5ecf679 Mon Sep 17 00:00:00 2001
From: Fschatbot <s.himanshu.sultania@fountainheadschools.org>
Date: Sat, 9 Dec 2023 21:28:49 +0530
Subject: [PATCH] Completed day 15 of year 2021

---
 2021/15.py | 83 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 83 insertions(+)
 create mode 100644 2021/15.py

diff --git a/2021/15.py b/2021/15.py
new file mode 100644
index 0000000..ee086af
--- /dev/null
+++ b/2021/15.py
@@ -0,0 +1,83 @@
+#!/usr/bin/env python
+# -*- coding: utf-8 -*-
+
+from heapq import heappush, heappop
+
+split_data = True
+completed = True
+raw_data = None # Not To be touched
+
+class Posv1:
+	def __init__(self, pos, map, prevRisk:int) -> None:
+		self.pos = pos
+		self.map = map
+		self.dist = (len(map[0]) - pos[0] - 1) + (len(map) - pos[1] - 1) # Manhattan distance
+		self.risk = prevRisk + int(map[pos[1]][pos[0]])
+	
+	def newMoves(self):
+		for dx, dy in [(0, 1), (0, -1), (1, 0), (-1, 0)]:
+			nx, ny = self.pos[0] + dx, self.pos[1] + dy
+			if 0 <= nx < len(self.map[0]) and 0 <= ny < len(self.map):
+				yield Posv1((nx, ny), self.map, self.risk)
+	
+	def __lt__(self, other:"Posv1") -> bool:
+		return self.risk + self.dist < other.risk + other.dist
+
+def part1(data):
+	# While the algorithm returns a path, its simply not good enough
+	queue = [Posv1((0, 0), data, 0)]
+	goal = (len(data[0]) - 1, len(data) - 1)
+	seen = []
+	while len(queue) > 0:
+		item = heappop(queue)
+		for newItem in item.newMoves():
+			if newItem.pos == goal:
+				return newItem.risk - int(data[0][0])
+			if newItem.pos in seen: continue # For now we will ignore this
+			heappush(queue, newItem)
+			seen.append(newItem.pos)
+
+def getMapRisk(map, pos):
+	mx, my = len(map[0]), len(map)
+	risk = int(map[pos[1] % my][pos[0] % mx]) # Getting the actual risk
+	add = (pos[1] // my) + (pos[0] // mx) # Getting the additional points
+	return (((risk + add) - 1) % 9 + 1) # Wrapping the risk back to original
+
+
+class Posv2:
+	def __init__(self, pos, map, prevRisk:int, nodes) -> None:
+		self.pos = pos
+		self.map = map
+		self.dist = (5*len(map[0]) - pos[0] - 1) + (5*len(map) - pos[1] - 1) # Manhattan distance
+		self.risk = prevRisk + getMapRisk(map, pos)
+		self.nodes = nodes + [pos]
+	
+	def newMoves(self):
+		for dx, dy in [(0, 1), (0, -1), (1, 0), (-1, 0)]:
+			nx, ny = self.pos[0] + dx, self.pos[1] + dy
+			if 0 <= nx < 5 * len(self.map[0]) and 0 <= ny < 5 * len(self.map):
+				yield Posv2((nx, ny), self.map, self.risk, self.nodes)
+	
+	def __lt__(self, other:"Posv2") -> bool:
+		return self.risk + self.dist < other.risk + other.dist
+
+def part2(data):
+	# Same thing as part1 expect for the few changes
+	# 2. Changed the map size (required change)
+	# 3. Everytime we get an item we add it to seen with its risk
+	#  ├> We add it to queue only if the risk is below what is seen
+	#  ╰> Due to this if we are running a queue item with risk above record we terminate that node
+	queue = [Posv2((0, 0), data, 0, [])]
+	goal = (5 * len(data[0]) - 1, 5 * len(data) - 1)
+
+	seen = {}
+	while len(queue) > 0:
+		item = heappop(queue)
+		if item.risk > seen.get(item.pos, float('Inf')): continue
+		for newItem in item.newMoves():
+			if newItem.pos == goal:
+				return newItem.risk - int(data[0][0])
+			
+			if newItem.pos not in seen or newItem.risk < seen[newItem.pos]:
+				heappush(queue, newItem)
+				seen[newItem.pos] = newItem.risk
\ No newline at end of file