Add day 15 solution

day-15/day-15.py

@@ -0,0 +1,96 @@
+#!/usr/bin/env python3
+from pathlib import Path
+
+
+def part_1(input):
+    result = 0
+    x_size = len(input[0].strip())
+    y_size = len(input)
+    nodes = {(x, y): int(v) for y, line in enumerate(input)
+             for x, v in enumerate(line.strip())}
+    start = (0, 0)
+    end = (x_size - 1, y_size - 1)
+    cost = {start: 0}
+    prev = {start: None}
+    queue = set([start])
+    done = set()
+    neighbors = set([(-1, 0), (0, -1), (0, 1), (1, 0)])
+    while len(queue):
+        cur_cost = None
+        for n in queue:
+            if cur_cost == None or cost[n] < cur_cost:
+                cur_cost = cost[n]
+                current = n
+        queue.remove(current)
+        (xc, yc) = current
+        next = set()
+        for (xn, yn) in neighbors:
+            nbr = (xc + xn, yc + yn)
+            if nbr in nodes and not nbr in done:
+                next.add(nbr)
+        for n in next:
+            next_cost = cur_cost + nodes[n]
+            if not n in cost or next_cost < cost[n]:
+                cost[n] = next_cost
+                prev[n] = current
+            queue.add(n)
+        done.add(current)
+    result = cost[end]
+    print("Part 1 result:", result)
+
+
+def part_2(input):
+    result = 0
+    x_size = len(input[0].strip())
+    y_size = len(input)
+    repeat = 5
+    nodes = {}
+    for y, line in enumerate(input):
+        for x, v in enumerate(line.strip()):
+            for i in range(repeat):
+                for j in range(repeat):
+                    xi = x + (x_size * i)
+                    yj = y + (y_size * j)
+                    vi = (int(v) + i + j)
+                    if 10 <= vi:
+                        vi -= 9
+                    nodes[(xi, yj)] = vi
+    start = (0, 0)
+    end = ((x_size * repeat) - 1, (y_size * repeat) - 1)
+    cost = {start: 0}
+    prev = {start: None}
+    queue = set([start])
+    done = set()
+    neighbors = set([(-1, 0), (0, -1), (0, 1), (1, 0)])
+    while len(queue):
+        cur_cost = None
+        for n in queue:
+            if cur_cost == None or cost[n] < cur_cost:
+                cur_cost = cost[n]
+                current = n
+        queue.remove(current)
+        (xc, yc) = current
+        next = set()
+        for (xn, yn) in neighbors:
+            x = xc + xn
+            y = yc + yn
+            if 0 <= x < (x_size * repeat) and 0 <= y < (y_size * repeat):
+                if not (x, y) in done:
+                    next.add((x, y))
+        for n in next:
+            next_cost = cur_cost + nodes[n]
+            if not n in cost or next_cost < cost[n]:
+                cost[n] = next_cost
+                prev[n] = current
+            queue.add(n)
+        done.add(current)
+    result = cost[end]
+    print("Part 2 result:", result)
+
+
+input = list()
+p = Path(__file__).with_name('input.txt')
+with open(p) as f:
+    input = f.readlines()
+    part_1(input)
+    part_2(input)