Add day3 problem + solution

day3/p1.nim

@@ -0,0 +1,40 @@
+import os
+import std/[strutils, enumerate]
+
+proc main() =
+  let fileName = paramStr(1)
+
+  # if we have a one, increase the counter
+  # otherwise for zero, decrease the counter for each bit
+  # this will give a positive number for 1 being the most
+  # common, and negative if 0 is the most common
+
+  var values = newSeq[int]()
+
+  for binary in fileName.lines:
+    if values.len == 0:
+      values.setLen(binary.len)
+
+    for (i, binVal) in enumerate(binary):
+      values[i] += (if binVal == '1': 1 else: -1)
+
+
+  var
+    gamma = newString(values.len)
+    epsilon = newString(values.len)
+
+  for (i, val) in enumerate(values):
+    if val > 0: # one is most common, so gamma is one, epsilon is zero
+      gamma[i] = '1'
+      epsilon[i] = '0'
+    elif val < 0: # zero is most common, so gamma is zero, epsilon is one
+      gamma[i] = '0'
+      epsilon[i] = '1'
+
+
+  let power = gamma.parseBinInt * epsilon.parseBinInt
+
+  echo "Power level: ", power
+
+
+main()