day 6, AWK solution, small optim

d06/exec.awk

@@ -2,16 +2,16 @@ BEGIN { W = 14 }
 {
 	for (i=1; i<=length($1); i++) {
 		window = substr($1,i,W)
-		# compare each char of window to all char of window
+		# 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; k<=W; k++) {
+			for (k=j+1; k<=W; k++) {
 				S+= (substr(window,j,1) == substr(window,k,1)) ? 1 : 0
 			}
 		}
-		if (S == W) {  # if each char match only with itsef
+		if (S == 0) {
 			print i + W - 1
-			next  # finish
+			next
 		}
 	}
 }