Add solution for day 17

day17/solution.py

@@ -0,0 +1,29 @@
+#!/usr/bin/python3
+
+# http://adventofcode.com/2017/day/17
+
+steps = 343
+
+cbuf = [0]
+curpos = 0
+
+for i in range(1,2017+1):
+	curpos = (curpos+steps) % len(cbuf) + 1 # will always be >= 1 (important for part 2)
+	cbuf[curpos:curpos] = [i]
+
+print("part 1", cbuf[cbuf.index(2017)+1])
+
+
+# Since every value is inserted AFTER the current position and 0 is the first element,
+# we know that there will never be a value inserted before the 0. Thus, we do not need to
+# apply the inserts to the buffer, we just watch for every iterations where a value at position 1 (after the 0) 
+# should be inserted. The last value is the value we are looking for
+# Not inserting elements to the buffer speeds up the algorithm
+curpos = 0
+
+for i in range(1,50000000+1):
+	curpos = (curpos+steps) % i + 1
+	if curpos == 1:
+		va0 = i
+
+print("part 2", va0)