A postal$-$code $($zipcode$)$ in the country SUA has the format

$$ DD$,$ where each is an upper$-$case letter of the English alphabet

and each D is a decimal digit; for example, P X $20$ is one such code.

Let each array element in A$[1],...,$ A$[$n$]$ be a string that contains the

SUA$-$postal$-$code of the destination of a letter that SUA postal service

has to deliver. A government agency that I cannot name is interested

in screening for $$suspicious$$ letters. In particular, they would like

to know if any two of the letters corresponding to A$[1],...,$ A$[$n$]$ have

destinations with identical postal$-$code $($i$.$e$.$ if there are any duplicates

in the n postal$-$codes$).$ Design an O$($n$)$ time algorithm for the problem.

It is enough if you clearly state the steps along with any relevant details