Insertion sort... Please help!

This is a discussion on Insertion sort... Please help! within the C++ Programming forums, part of the General Programming Boards category; So for an assignment I'm supposed to have my insertion sort program take numbers from a file (in this case ...

  1. #1
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    Insertion sort... Please help!

    So for an assignment I'm supposed to have my insertion sort program take numbers from a file (in this case infile.txt) and sort them using insertion sort then output the array.

    This is what I currently have:
    Code:
    #include <fstream>
    #include <iostream>
    using namespace std;
    
    
    int main()
    {
       ifstream fin("infile.txt");
       int a[6], length, number, i;
            for(int j=1;j<length;j++)
            {
            number=a[j];
            i=j-1;
                    while(a[i]>number && i>=0)
                    {
                            a[i+1]=a[i];
                            i--;
                    }
            a[i+1]=number;
            }
    
       cout << a[i] << "\n";
       return 0;
    }
    When the infile.txt file lists the numbers:
    5
    6
    98
    7
    5
    6
    1
    8
    6
    4

    However, as an output I am just getting the number 13... Does anyone know why this would be and how I would go about fixing it?
    THANK YOU SO MUCH!!!!!!!!!!!

  2. #2
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    im not good at programming much and im not familiar with file i/o but where are you recording the numbers from the file

  3. #3
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    you need to fill int a[6], length, number, i, with some values before you can use them. (eg. by taking input from fin)

  4. #4
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    and im guessing you would get a different number besides 13 everytime, maybe idk or no output

  5. #5
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    Quote Originally Posted by cyberfish View Post
    you need to fill int a[6], length, number, i, with some values before you can use them. (eg. by taking input from fin)
    Do you mean like declare length = to a specific number?

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    i dont know the syntax or anything but get all those numbers from the file stream into int array!

  7. #7
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    I'll have to google that one :-p

  8. #8
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    Ok well I dont really get wut u want to do... But if you wanna read in a file and put the values in an array here is a simple way to do it :
    Code:
    #include <iostream>
    #include <vector>
    #include <fstream>
    using namespace std;
    
    int main(int argc, char *argv[])
    {
    	string filename="file";
    	int numbers;
    	vector <int> array;   
       	
       	ifstream Read;
       	Read.open(filename.c_str());
       
       	if(Read.fail()) 
    	{
          		cerr << "Error couldnt open the file" << filename << endl;
          		exit(EXIT_FAILURE);
       	}
       		
       	while(Read >> numbers) 
       	{
          		array.push_back(numbers);	
       	}
       
       	for(int i=0;i<array.size();i++)
       	{
       		cout << array[i]<<endl;
       	}
    
                  Read.close();
    return 0;
    }
    And about sorting em... I dont get what you want to do...
    Last edited by eezaa; 11-29-2007 at 05:39 PM.

  9. #9
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    he is trying to sort those numbers in order using "insertion" method,,there are a couple other methods

    i remember learning about them back in high school, i dont remember if that was the efficient method but w/e

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  11. #11
    Algorithm Dissector iMalc's Avatar
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    The first problem is that you're not actually reading anything in from the file.
    The second problem is that you're only outputting one number (you need a loop to output them all).

    The sorting algorithm itself looks correct, from memory.
    My homepage
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  12. #12
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    Also, if you want to sort 10 numbers, you probably need an array bigger than 6?

    --
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    Please don't PM me for help - and no, I don't do help over instant messengers.

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