Thread: single for loop --- two conditions??

  1. #1
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    single for loop --- two conditions??

    How do you write the following as two nested loops?

    Code:
    for (int low = 0, high = n - 1; low < high; low++, high--)

  2. #2
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    It can't be written as nested loops without totally changing what it does.
    It is by nature a single-dimensional loop.
    Why do you think you want a double loop?
    Last edited by john.c; 07-14-2021 at 11:10 AM.
    The best argument against democracy is a five minute conversation with the average voter. - Churchill

  3. #3
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    General rule: for is only a clever way to write while loops. With your example:
    Code:
    for (int i = 0, j = n - 1; i < j; i++, j--)
      doSomething();
    Is the same as:
    Code:
    /* block, because i and j are local to the loop */
    {
      int i = 0, j = n - 1;
    
      while ( i < j )
      {
        doSomething();
    
        i++, j--;
      }
    }

  4. #4
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    I don't think you want that as two loops, because that would change the behavior in ways you don't expect. However, you could factor the "high" variable out as a function of the "low" variable:

    Code:
     
    for (int low = 0; low < n / 2; ++low) {
         int high = n - 1 - low;
    
        // etc.
    }

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