aoc2022/d03/part2.awk

NR%3==1 {split($0,arr,"");for(a in arr){A[arr[a]]=1}}
NR%3==2 {split($0,arr,"");for(a in arr){B[arr[a]]=1}}
NR%3==0 {
	split($0,arr,"")
	for (a in arr) {
		c = arr[a]
		if ((c in A)&&(c in B)) {comm = c}
	}
	S += index("abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ", comm)
	delete A
	delete B
}
END {print S}