day6, a set kills all

d06/exec1.awk

@@ -0,0 +1,17 @@
+{ N=0; # use -vW=4 or 14
+	for (i=1; ; i++) {
+		window = substr($0,i,W)
+		# compare each char of the window to rest of the window
+		S = 0  # to count match
+		for (j=1; j<W; j++) {
+			for (k=j+1; k<=W; k++) {
+				N++
+				S+= (substr(window,j,1) == substr(window,k,1)) ? 1 : 0
+			}
+		}
+		if (S == 0) {
+			print i + W - 1, "(" N " loops)"
+			next
+		}
+	}
+} # O(N*W^2)

d06/exec2.awk

@@ -1,4 +1,4 @@
-{ j=0; # use -vW=4 or 14
+{ N=0; j=0; # use -vW=4 or 14
 	for (i=1; ; i++) {
 		c = substr($0,i,1);
 		# look backward for a "new j" > j

d06/exec3.awk

@@ -0,0 +1,13 @@
+{ # use -vW=4 or 14
+	for (i=1; ; i++) {
+		window = substr($0,i,W)
+		for (j=1; j<=W; j++) {  # populate a Set
+			A[substr(window,j,1)]=1
+		}
+		if (length(A) == W) {
+			print i + W - 1
+			next
+		}
+		delete A
+	}
+} # O(N*W*log2(W))