Exercises (from Ravi Sethi)

1.1 In words, describe a program to read a sequence of integers

and to write the integers that appear one or more times in

the input sequence. For example, if the input sequence is

617, 201, 415, 201, then 201 must appear just once in the

output.

1.2 Describe a program that produces the output sequence

of Exercise 1.1 incrementally. That is, an integer that is seen

for the first time in the input is written before any more integers

are read.