ACM Problem Confusion

This is a discussion on ACM Problem Confusion within the C Programming forums, part of the General Programming Boards category; Hello: I am attempting at this Online Judge problem: http://icpcres.ecs.baylor.edu/online...m&problem=1464 The mathematics calculation part is extremely easy; but I do ...

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    ACM Problem Confusion

    Hello:
    I am attempting at this Online Judge problem:
    http://icpcres.ecs.baylor.edu/online...m&problem=1464

    The mathematics calculation part is extremely easy; but I do not understand what type of input will be given to my problem; therefore I do not know how to do this problem.
    Am I expecting the input to be from a flat text file? If so; then I would need to go through every line and calculate the answer; put it into an array and output the entire array at the end... I would keep doing that until the EOF character right? How do I look for the EOF character?
    Sorry for the beginner questions; but I am really confused by what this problem really wants... Any input would be greatly appreciated!

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    C++ Witch laserlight's Avatar
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    Am I expecting the input to be from a flat text file?
    That is possible. It is also possible that it is from stdin perhaps by input redirected from a file.

    If so; then I would need to go through every line and calculate the answer; put it into an array and output the entire array at the end... I would keep doing that until the EOF character right?
    Yes.

    How do I look for the EOF character?
    That depends on how you read the input. For example, fscanf() returns EOF if EOF is reached. Note that EOF is not really a character.
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    Most online code tests are based on redirecting a text file as input and redirecting the apps output to a result file, then comparing the result with a template result. The input may be the same all the time, or generated at runtime, and the template result generated by a "known good" application.

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    Thanks for the help guys.
    However; so I am going to assume the input is from a text file... then what would the loop for the input look like? Would I use a "do-while" loop or another one? I am thinking I would do something like this:
    Code:
    do
      {
        /* calculate and get result */
        //put result into array
      }
    while (*test for EOF*)
    But the obvious questions are... how would I make the array if I have no idea how big it will be? I thought dynamic arrays did not exist in C...
    Also; and what would the test for EOF look like for redirected text files?


    Thanks

  5. #5
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    Why do you need to put the result in an array? You should be fine to just output the result when you have finished one calculation.

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    Mats
    Compilers can produce warnings - make the compiler programmers happy: Use them!
    Please don't PM me for help - and no, I don't do help over instant messengers.

  6. #6
    and the Hat of Guessing tabstop's Avatar
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    Didn't you ask this problem before?

    Do not store the answers. Print the result as soon as it is computed.

    As for the reading in of numbers: the test for EOF doesn't change depending on whether it's redirected from stdin or read using fscanf (or similar). When you have tried to read a number that isn't there, feof is set true for that file handle.

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    All input for those problems will be redirected from a file to stdin. A basic skeleton for a competition problem typically looks like this:
    Code:
    #include <stdlib.h>
    #include <stdio.h>
    
    int main(void) {
       int num, answer;
    
       while (1) {
          // read input
          scanf("%d", &num);
    
          // handle termination condition
          if (num == 0) break;
    
          // do calculations
          answer = num * 2;
    
          // print answer
          printf("%d\n", answer);
       }
    
       return 0;
    }
    To test your program, type their sample test case into a text file (input.txt), save it, and run your program like this:

    prog < input.txt

    Some competitions require you to print EXACTLY the right number of newline characters (meaning your last output would not have a newline after it). The Online Judge problems do not (from what I have seen), so make sure you print a single newline after every output (unless the problem states otherwise). If you fail to do this, your submission will get flagged "wrong answer", and it will probably drive you crazy.

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