Add day 6 solutions

day6.chpl

@@ -0,0 +1,17 @@
+use IO;
+
+config const numChars = 4;
+
+var theBytes: bytes;
+stdin.read(theBytes);
+
+var indices: [0..<26] int = -numChars;
+
+for (char, idx) in zip(theBytes.these() - b"a"[0], 0..) do {
+  indices[char] = idx;
+
+  if + reduce (indices > idx - numChars) == numChars {
+    writeln(idx + 1);
+    break;
+  }
+}