seen to 0 to act as a bit mask.c in the sentence.
a. Calculate the index i by subtracting the ASCII value of 'a' from the ASCII value of c.
b. Create a bit mask mask by left shifting 1 by i positions.
c. Update seen by performing a bitwise OR with mask.seen is equal to (1 << 26) - 1, which represents all 26 bits set. If true, return true; otherwise, return false.