Define a function that takes in two non-negative integers $a$
and $b$
and returns the last
decimal digit of $a^b$
. Note that $a$
and $b$
may be very large!
For example, the last decimal digit of $9^7$
is $9$
, since $9^7 = 4782969$
. The last decimal
digit of $({2^{200}})^{2^{300}}$
, which has over $10^{92}$
decimal digits, is $6$
. Also,
please take $0^0$
to be $1$
.
You may assume that the input will always be valid.
lastDigit(new BigInteger("4"), new BigInteger("1")) // returns 4
lastDigit(new BigInteger("4"), new BigInteger("2")) // returns 6
lastDigit(new BigInteger("9"), new BigInteger("7")) // returns 9
lastDigit(new BigInteger("10"), new BigInteger("10000000000")) // returns 0