2021/10/both.nim

@@ -0,0 +1,83 @@
+import
+  std/strformat,
+  std/strutils,
+  std/tables
+  
+when defined(second):
+  import std/algorithm
+
+import
+  ../../adventofcode
+
+let input = adventofcode.getInput(2021, 10)
+let lines = input.splitLines()
+
+const chunkSymbols = (
+  open: {
+    '(': ')',
+    '[': ']',
+    '{': '}',
+    '<': '>'
+  }.toTable(),
+  close: {
+    ')': '(',
+    ']': '[',
+    '}': '{',
+    '>': '<'
+  }.toTable()
+)
+
+when not defined(second):
+  const chunkScores = {
+    ')': 3,
+    ']': 57,
+    '}': 1197,
+    '>': 25137
+  }.toTable()
+else:
+  const chunkScores = {
+    ')': 1,
+    ']': 2,
+    '}': 3,
+    '>': 4
+  }.toTable()
+
+var score = 0
+when defined(second):
+  var lineScores: seq[int]
+
+for line in lines:
+  var chunks: seq[char]
+
+  block abortLine: 
+    for it in line:
+      if chunkSymbols.open.hasKey it:
+        chunks.add it
+      
+      if chunkSymbols.close.hasKey it:
+        let expectedSymbol = chunkSymbols.open[chunks[^1]]
+        if it == expectedSymbol:
+          discard chunks.pop()
+        else:
+          # Line is corrupted.
+          when not defined(second):
+            score += chunkScores[it]
+          break abortLine
+          
+    # Complete line by closing chunks
+    when defined(second):
+      var lineScore = 0
+
+      for idx in 0 .. chunks.high():
+        let it = chunks[chunks.high() - idx]
+        let closeSym = chunkSymbols.open[it]
+        lineScore *= 5
+        lineScore += chunkScores[closeSym]
+
+      lineScores.add lineScore
+
+when defined(second):
+  lineScores.sort()
+  score = lineScores[lineScores.len() div 2]
+
+echo fmt"Answer: {score}"