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C++ helpI have started learning c++ and I need help. I need to write a
program, the question is as follows. At a post office, there are a certain number of 2, 7, and 9cents stamps, now, given a total number of cents required, find the correct and most effective combination of stamps. meaning that if you were to need 14cents, the correct output should be 2 seven cents not 7 two cents. the program is to use functions, and at first I thought I could use bisection searching, but that didn't go very well. I think we are suppose to use call-by-references as well, except I haven't figured out how to do that yet. Any help would be greatly appreciated. Thanks Davy |

Re: C++ helpdavy.zou@brentwood.bc.ca wrote:
> I have started learning c++ and I need help. I need to write a > program, the question is as follows. > > At a post office, there are a certain number of 2, 7, and 9cents > stamps, now, given a total number of cents required, find the correct > and most effective combination of stamps. > > meaning that if you were to need 14cents, the correct output should be > 2 seven cents not 7 two cents. > > the program is to use functions, and at first I thought I could use > bisection searching, but that didn't go very well. I think we are > suppose to use call-by-references as well, except I haven't figured > out how to do that yet. > > Any help would be greatly appreciated. > Post an attempt and you will get some help. We don't do homework here, but we are happy to help with problems in your homework code. -- Ian Collins. |

Re: C++ helpOn Mar 3, 5:55 pm, Ian Collins <ian-n...@hotmail.com> wrote:
> davy....@brentwood.bc.ca wrote: > > I have started learning c++ and I need help. I need to write a > > program, the question is as follows. > > > At a post office, there are a certain number of 2, 7, and 9cents > > stamps, now, given a total number of cents required, find the correct > > and most effective combination of stamps. > > > meaning that if you were to need 14cents, the correct output should be > > 2 seven cents not 7 two cents. > > > the program is to use functions, and at first I thought I could use > > bisection searching, but that didn't go very well. I think we are > > suppose to use call-by-references as well, except I haven't figured > > out how to do that yet. > > > Any help would be greatly appreciated. > > Post an attempt and you will get some help. We don't do homework here, > but we are happy to help with problems in your homework code. > > -- > Ian Collins. I wasn't asking anyone to do my homework. I just need someone to point me in the right direction. |

Re: C++ helphere is the code I first came up with, obviously it doesn't work,
#include <iostream.h> #include <math.h> int centscalculation (int x, int y, int z); int computecent (int x, int y, int z); int centscalculation (int x, int y, int z) { double low=0, high=1, guessedcent, calculatedcent; const double epsilon=0.0001; for (;;) { guessedcent=(low+high)/2; if ((high-low)<(2*epsilon)) { return guessedcent; } centscalculation=computecent (x, y, z); if (calculatedcent==guessedcent) { return guessedcent; } if (calculatedcent>guessedcent) { low=guessedcent; } else { high=guessedcent; } } } int computecent (int x, int y, int z) { int a=2, b=7, c=9; return x*a+y*b+z*c; } void main () { int cents, a=2, b=7, c=9, x, y, z, ans; //a has value of 2, b has 7, c has 9 while (true) { cout<<"Enter cents, 0 to terminate: "<<endl; cin>>cents; if (cents<0) { cout<<"Error."<<endl; } if (cents=0) { break; } ans=centscalculation (x, y, z); cout<<"answer is "<<ans<<endl; } } |

Re: C++ helpOn 3 Mar, 23:02, davy....@brentwood.bc.ca wrote:
> On Mar 3, 5:55 pm, Ian Collins <ian-n...@hotmail.com> wrote: > > davy....@brentwood.bc.ca wrote: > > > I have started learning c++ and I need help. I need to write a > > > program, the question is as follows. > > > > At a post office, there are a certain number of 2, 7, and 9cents > > > stamps, now, given a total number of cents required, find the correct > > > and most effective combination of stamps. > > > > meaning that if you were to need 14cents, the correct output should be > > > 2 seven cents not 7 two cents. > > > > the program is to use functions, and at first I thought I could use > > > bisection searching, but that didn't go very well. I think we are > > > suppose to use call-by-references as well, except I haven't figured > > > out how to do that yet. > > > > Any help would be greatly appreciated. > > > Post an attempt and you will get some help. We don't do homework here, > > but we are happy to help with problems in your homework code. > I wasn't asking anyone to do my homework. I just need someone to point > me in the right direction. The FAQ is at http://www.parashift.com/c++-faq-lite/ but it seems to be down at the moment. When it comes back to life, the FAQ you want is 5.8. As Ian says, there are plenty of people here willing and able to help you, but none of them are mind-readers. Nobody can help you without knowing what your problem is. FAQ 5.8 explains how to get that help. In summary: Post the actual code you are having problems with, not a description of the code. Post *minimal* code - i.e. the *smallest possible* program that exhibits your problem. Post *compileable* code - i.e. copied and pasted *directly* from your editor into your message For code that does not compile and you don't understand why, copy and past the error messages directly from your compiler and make it clear which statement(s) the error refers to. For a program that compiles and runs but doesn't behave as you expect, post the inputs to the program, the actual outputs and your expected outputs. Without all this, nobody can be sure they are recreating exactly the situation you have and be sure they are answering the right question. HTH Gavin Deane |

Re: C++ helpOn Mar 3, 6:23 pm, "Gavin Deane" <deane_ga...@hotmail.com> wrote:
> On 3 Mar, 23:02, davy....@brentwood.bc.ca wrote: > > > > > On Mar 3, 5:55 pm, Ian Collins <ian-n...@hotmail.com> wrote: > > > davy....@brentwood.bc.ca wrote: > > > > I have started learning c++ and I need help. I need to write a > > > > program, the question is as follows. > > > > > At a post office, there are a certain number of 2, 7, and 9cents > > > > stamps, now, given a total number of cents required, find the correct > > > > and most effective combination of stamps. > > > > > meaning that if you were to need 14cents, the correct output should be > > > > 2 seven cents not 7 two cents. > > > > > the program is to use functions, and at first I thought I could use > > > > bisection searching, but that didn't go very well. I think we are > > > > suppose to use call-by-references as well, except I haven't figured > > > > out how to do that yet. > > > > > Any help would be greatly appreciated. > > > > Post an attempt and you will get some help. We don't do homework here, > > > but we are happy to help with problems in your homework code. > > I wasn't asking anyone to do my homework. I just need someone to point > > me in the right direction. > > The FAQ is athttp://www.parashift.com/c++-faq-lite/but it seems to > be down at the moment. When it comes back to life, the FAQ you want is > 5.8. As Ian says, there are plenty of people here willing and able to > help you, but none of them are mind-readers. Nobody can help you > without knowing what your problem is. FAQ 5.8 explains how to get that > help. In summary: > > Post the actual code you are having problems with, not a description > of the code. > Post *minimal* code - i.e. the *smallest possible* program that > exhibits your problem. > Post *compileable* code - i.e. copied and pasted *directly* from your > editor into your message > For code that does not compile and you don't understand why, copy and > past the error messages directly from your compiler and make it clear > which statement(s) the error refers to. > For a program that compiles and runs but doesn't behave as you expect, > post the inputs to the program, the actual outputs and your expected > outputs. > > Without all this, nobody can be sure they are recreating exactly the > situation you have and be sure they are answering the right question. > > HTH > Gavin Deane Thanks alot. |

Re: C++ help<davy.zou@brentwood.bc.ca> wrote:
> here is the code I first came up with, obviously it doesn't work, <snip> Think about dividing the available amount by 9, 7 and 2 in that order. I am not sure that is the right answer in all cases, but you can expand on it if needed. Look up the modulo operator (%). See the Wikipedia entry for modulo.. |

Re: C++ helposmium wrote:
> <davy.zou@brentwood.bc.ca> wrote: > >> here is the code I first came up with, obviously it doesn't work, > > <snip> > > Think about dividing the available amount by 9, 7 and 2 in that order. I > am not sure that is the right answer in all cases, but you can expand on > it if needed. [snip] I am not so sure that this looks like a promissing line of attack. There seems to be a little more to the problem. What is the answer for 10 and how do you find it through the division sequence? What about 35? Best Kai-Uwe Bux |

Re: C++ helpOn Mar 3, 6:43 pm, "osmium" <r124c4u...@comcast.net> wrote:
> <davy....@brentwood.bc.ca> wrote: > > here is the code I first came up with, obviously it doesn't work, > > <snip> > > Think about dividing the available amount by 9, 7 and 2 in that order. I am > not sure that is the right answer in all cases, but you can expand on it if > needed. Look up the modulo operator (%). See the Wikipedia entry for > modulo.. THANK YOU! dividing it by 9, 7, and 2! that is ingenious! |

Re: C++ helpdavy.zou@brentwood.bc.ca wrote:
> I have started learning c++ and I need help. I need to write a > program, the question is as follows. > > At a post office, there are a certain number of 2, 7, and 9cents > stamps, now, given a total number of cents required, find the correct > and most effective combination of stamps. > > meaning that if you were to need 14cents, the correct output should be > 2 seven cents not 7 two cents. > > the program is to use functions, and at first I thought I could use > bisection searching, but that didn't go very well. I think we are > suppose to use call-by-references as well, except I haven't figured > out how to do that yet. > > Any help would be greatly appreciated. > > Thanks > Davy > This is a variation of the bin packing problem. I've developed C++ code which can solve this problem for all solutions. It is also capable of handling target ranges as well, and multiples thereof. It's known to be a hard problem to create an efficient algorithm for. JB |

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