Max Digits

This is a discussion on Max Digits within the C Programming forums, part of the General Programming Boards category; Hi, I am writing a C program that will allow me to determine the maximum number of digits that a ...

  1. #1
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    Max Digits

    Hi,
    I am writing a C program that will allow me to determine the maximum number of digits that a value can have to be within the range 0..m.

    for example:

    if m=23
    max number of digits =1
    Actual range 0..9

    if m=379
    max number of digits =2
    Actual range 0..99

    if m=453638923
    max number of digits =8
    Actual range 0..99999999

    where 9 is a digit not a value...

    firstly I dont want code but could someone explain the above theory as I just dont get it....

  2. #2
    and the hat of wrongness Salem's Avatar
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    log10(23) = 1.xxx
    log10(379) = 2.xxx

  3. #3
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    I dont understand. Isn't the value 20 within the range of 0...23? 20 has 2 digits.

    What you need to do to find out the max digits is to find the number of digits your 'm' has. I really dont know how to explain theory, but I can give you an example...


    12345 / 10 = 1234.5
    12345 / 100 = 123.45
    12345 / 1000 = 12.345
    .
    .
    .

    remember that if both values are ints, then the fractional portion of the values will get truncated (cut off)

  4. #4
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    Salem made use of the logarithm function, it is in some way the inverse of the power function. Example:

    10^2 = 100
    log10 (100) = 2

    Note that the base is 10, that's why it goes OK. For numbers with base 10, the total number of digits can be calculated as:

    nr_of_digits = (int) log10 (N) + 1

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