Port day 3 to nim

day03.nim

@@ -0,0 +1,48 @@
+import intsets, sequtils, strscans, strutils
+
+var
+    claims: seq[tuple[id, x, y, width, height: int]]
+    max_x, max_y = int.low
+    min_x, min_y = int.high
+
+for line in readFile("data/03.txt").strip.splitlines:
+    var id, x, y, width, height: int
+    if not line.scanf("#$i @ $i,$i: $ix$i", id, x, y, width, height):
+        raise newException(Defect,  "Invalid input line: " & line)
+    claims.add((id, x, y, width, height))
+    min_x = min(min_x, x)
+    max_x = max(max_x, x + width)
+    min_y = min(min_y, y)
+    max_y = max(max_y, y + height)
+
+let
+    x_range = 1 + max_x - min_x
+    y_range = 1 + max_y - min_y
+
+var
+    cells = newSeq[int](x_range * y_range)
+    ids = initIntSet()
+    overlaps = 0
+
+for claim in claims:
+    var collision = false
+    for x in claim.x..claim.x + claim.width - 1:
+        for y in claim.y..claim.y + claim.height - 1:
+            var
+                index = (y - min_y) * y_range + (x - min_x)
+                previous = cells[index]
+            if previous == 0:
+                cells[index] = claim.id
+            elif previous == -1:
+                collision = true
+            else:
+                collision = true
+                overlaps.inc
+                if previous in ids:
+                    ids.excl(previous)
+                cells[index] = -1
+    if not collision:
+        ids.incl(claim.id)
+
+echo overlaps
+echo toSeq(ids.items)[0]