Read input numbers separated by spaces

Question

This may be a total beginner s question  but I have yet to find an answer that works for me   Currently  I m writing a program for a class that takes in a user s input  which can be one or more numbers separated by spaces   then determines whether the number is prime  perfect  or neither  If the number is perfect  then it will display the divisors   Thus far  I ve already written the code for the prime  perfect  and listing the divisors  I m stuck on the input portion of my program  I don t know how to get the input that s separated by spaces to go through my loops one at a time   This is my current program   cout lt  lt  Enter a number  or numbers separated by a space  between 1 and 1000   lt  lt endl  cin gt  gt num   while  divisor lt  num      if num divisor  0                cout lt  lt divisor lt  lt endl          total total divisor          divisor              else divisor    if total  num 2      cout lt  lt  The number you entered is perfect   lt  lt endl  else cout lt  lt  The number you entered is not perfect   lt  lt endl    if num  2  num  3  num  5  num  7      cout lt  lt  The number you entered is prime   lt  lt endl   else if num 2  0  num 3  0  num 5  0  num 7  0      cout lt  lt  The number you entered is not prime   lt  lt endl  else cout lt  lt  The number you entered is prime   lt  lt endl   return 0    It works  but only for a single number  If anyone could help me to get it to be able to read multiple inputs separated by spaces  it d be greatly appreciated  Also  just a side note  I do not know how many numbers will be entered  so I can t just make a variable for each one  It will be a random amount of numbers   Thanks

User · Answer

You ll want to    Read in an entire line from the console Tokenize the line  splitting along spaces  Place those split pieces into an array or list Step through that array list  performing your prime perfect etc tests    What has your class covered along these lines so far

User · Answer

int main     int sum   0  cout  lt  lt   quot enter number quot   lt  lt  endl  int i   0  while  true        cin  gt  gt  i      sum    i        cout  lt  lt  i  lt  lt  endl      if  cin peek        n             break                cout  lt  lt   quot result   quot   lt  lt  sum  lt  lt  endl  return 0     I think this code works  you may enter any int numbers and spaces  it will calculate the sum of input ints

User · Answer

I would recommend reading in the line into a string  then splitting it based on the spaces  For this  you can use the getline      function  The trick is having a dynamic sized data structure to hold the strings once it s split  Probably the easiest to use would be a vector    include  lt string gt   include  lt vector gt        string rawInput    vector lt String gt  numbers    while  getline  cin  rawInput                  numbers push back rawInput         So say the input looks like this   Enter a number  or numbers separated by a space  between 1 and 1000  10 5 20 1 200 7   You will now have a vector  numbers  that contains the elements    10   5   20   1   200   7     Note that these are still strings  so not useful in arithmetic  To convert them to integers  we use a combination of the STL function  atoi       and because atoi requires a c-string instead of a c   style string  we use the string class  c str   member function   while  numbers empty        string temp   numbers pop back     removes the last element from the string   num   atoi  temp c str        re-used your  num  variable from your code         do stuff     Now there s some problems with this code  Yes  it runs  but it is kind of clunky  and it puts the numbers out in reverse order  Lets re-write it so that it is a little more compact    include  lt string gt      string rawInput  cout  lt  lt   Enter a number  or numbers separated by a space  between 1 and 1000    lt  lt  endl  while  getline  cin  rawInput             num   atoi  rawInput c str             do your stuff     There s still lots of room for improvement with error handling  right now if you enter a non-number the program will crash   and there s infinitely more ways to actually handle the input to get it in a usable number form  the joys of programming    but that should give you a comprehensive start      Note  I had the reference pages as links  but I cannot post more than two since I have less than 15 posts     Edit  I was a little bit wrong about the atoi behavior  I confused it with Java s string- Integer conversions which throw a Not-A-Number exception when given a string that isn t a number  and then crashes the program if the exception isn t handled  atoi    on the other hand  returns 0  which is not as helpful because what if 0 is the number they entered  Let s make use of the isdigit      function  An important thing to note here is that c   style strings can be accessed like an array  meaning rawInput 0  is the first character in the string all the way up to rawInput length - 1     include  lt string gt   include  lt ctype h gt      string rawInput  cout  lt  lt   Enter a number  or numbers separated by a space  between 1 and 1000    lt  lt  endl  while  getline  cin  rawInput             bool isNum   true    for int i   0  i  lt  rawInput length    amp  amp  isNum    i          isNum   isdigit  rawInput i           if isNum          num   atoi  rawInput c str               do your stuff       else     cout  lt  lt  rawInput  lt  lt    is not a number    lt  lt  endl      The boolean  true false or 1 0 respectively  is used as a flag for the for-loop  which steps through each character in the string and checks to see if it is a 0-9 digit  If any character in the string is not a digit  the loop will break during it s next execution when it gets to the condition   amp  amp  isNum   assuming you ve covered loops already   Then after the loop  isNum is used to determine whether to do your stuff  or to print the error message

User · Answer

By default  cin reads from the input discarding any spaces  So  all you have to do is to use a do while loop to read the input more than one time   do      cout lt  lt  Enter a number  or numbers separated by a space  between 1 and 1000   lt  lt endl     cin  gt  gt  num         reset your variables        your function stuff  calculations    while  true      or some condition

[c++] Read input numbers separated by spaces

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