index | submit | rank | book

hi – Hello, You!

Hello, <You>!

Write a program that reads several names from the standard input device and, for each name, prints Hello, <Name>! on the standard output device. The standard input and output devices are usually the keyboard and screen of a command line session.

$ ./hi
Hello, John!
Hello, Mary!
Hello, Smith!

Input and output

Names are provided one per line, and do not contain spaces. Names are composed of letters of the English alphabet or dashes (-), and have no more than 30 characters.

Example input


Example output

Hello, John!
Hello, Mary!
Hello, Smith!


Submit your solution to be graded according to the following list:


If you do not know where to start, read the Computer Science by Example book. First, setup your environment then learn the programming basics. Here are some hints:

  1. Automated judge: Keep in mind that when your program is submitted it will not be run by a human but instead by an automated judge. Instructions should be followed exactly or the judge will not give you a full score.

    Your program should not print messages like Please type your name:. Instead, just print the required message for each name followed by a line break as in the example output.

  2. Produce output as you go: You do not need to accumulate names and then produce everything at the end. It is enough to produce output as you go. As soon as you read a name, write the corresponding hello message to standard output.

  3. Detecting the end of file. In this exercise, input is terminated by the end-of-file (EOF). Here are ways to detect EOF in C, Python and Haskell:

    • In C. The scanf function returns the numbers of elements read from stdin. Since this exercise requires you to read one number each line, you can compare scanf’s result to one as a while condition:

        while (scanf(...)==1) {

      Which translates to, “while you’re able to read 1 item from standard input, do …”

    • In Python. The pattern for line in sys.stdin: can be used to create a loop where a file is processed line by line until the end-of-file (EOF).

    • In Haskell. You can use interact to declare the main function and implement your solution as a function from String to String:

        io :: String -> String
        io = ...
        main :: IO
        main = interact io

      EOF is then represented as the nil list constructor ("" or []) at the end of the argument String.

    On the terminal, you can simulate the end-of-file (EOF) by holding “Ctrl” and pressing “D”, i.e., Ctrl-D.

  4. Redirecting input: On most systems (Windows / Linux / OS X), it is possible to redirect the standard input and output of your program to files, like so:

     $ ./repeat <inputfile.txt >outputfile.txt

    If you create a plain text file with the “example input”, the above command should produce a plain text file with the “example output”.

    This is actually how the automated judge runs your program.

  5. Easier exercises: If you have difficulty with this exercise, try the repeat and hi1 exercises first.

try first: repeat hi1

try next: age swap

index | submit | rank | book

Copyright © 2020-2021 Rudy Matela
All rights reserved