How do I skip over zero elements in an array?

This is a discussion on How do I skip over zero elements in an array? within the C Programming forums, part of the General Programming Boards category; I'm initializing an array with a value of [9]. The user can either enter all 10 values or enter a ...

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    How do I skip over zero elements in an array?

    I'm initializing an array with a value of [9]. The user can either enter all 10 values or enter a negative number to stop the array. Then I want to average all of the elements in the array, but if the user enters a negative number to stop the array, then it makes the rest of the values in the array zero. How would I code it to make sure that the zero values do not get averaged?

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    Quote Originally Posted by Roon Hapoon View Post
    I'm initializing an array with a value of [9]. The user can either enter all 10 values or enter a negative number to stop the array. Then I want to average all of the elements in the array, but if the user enters a negative number to stop the array, then it makes the rest of the values in the array zero. How would I code it to make sure that the zero values do not get averaged?
    First of all, if you are creating an array with [9] indexes, then a user can only enter 9 values -- not 10.

    Why not store -1 in the index, and then when you average the numbers, don't include any index with a -1.
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    Quote Originally Posted by bithub View Post
    Why not store -1 in the index, and then when you average the numbers, don't include any index with a -1.
    But how would I do that? With an if statement?

    for (x = 0; x < 10; x++)
    {
    avg = (array[x] + avg) / x;
    if (array[x] == -1)

    but then what? That's the part I just don't get :\

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    So, loop until the index reaches 10, or the current element is negative.
    Quote Originally Posted by Bjarne Stroustrup (2000-10-14)
    I get maybe two dozen requests for help with some sort of programming or design problem every day. Most have more sense than to send me hundreds of lines of code. If they do, I ask them to find the smallest example that exhibits the problem and send me that. Mostly, they then find the error themselves. "Finding the smallest program that demonstrates the error" is a powerful debugging tool.
    Look up a C++ Reference and learn How To Ask Questions The Smart Way

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    Quote Originally Posted by Roon Hapoon View Post
    But how would I do that? With an if statement?

    for (x = 0; x < 10; x++)
    {
    avg = (array[x] + avg) / x;
    if (array[x] == -1)

    but then what? That's the part I just don't get :\
    Use the break statement to exit your loop when you reach a -1.
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    Math Note: Average is the sum of the elements divided by the number of elements.

    I have no idea what your code is doing.

    Tim S.

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    Quote Originally Posted by Roon Hapoon View Post
    But how would I do that? With an if statement?

    for (x = 0; x < 10; x++)
    {
    avg = (array[x] + avg) / x;
    if (array[x] == -1)

    but then what? That's the part I just don't get :\
    I would try something like...
    Code:
    int array[10];
    int avg ;
    
    // user enters values
    
    avg = 0;
    for (int x = 0; x < 10; x++)
      { if (array[x] == -1)  
            { avg /= x;
              break; }
         avg += array[x]; }

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    I wouldn't calculate a "running" average. Unless you specifically need to keep a running average, don't do it - it's just extra calculation for nothing.

    taking your code:
    Code:
    for (x = 0; x < 10; x++)
    {
    avg = (array[x] + avg) / x;
    if (array[x] == -1)
    
    and removing the running average and adding a sum:
    for(x = 0, sum = 0; x < 10; x++) 
    {
      if(array[x] > -1) 
        sum = sum + array[x];
      else
        break;
    }
    //now calculate the sum, just once:
    average = sum/x;
    The standard idiom or practice in C, with arithmetic like: sum = sum + someNumber, is to use the shorthand: sum += someNumber. Don't be surprised if you see C code like that - it's very common. That applies to subtraction, multiplication, and division, as well as addition.

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