Array trouble

This is a discussion on Array trouble within the C++ Programming forums, part of the General Programming Boards category; Ok, I have a 2d array, and am reading the numbers from a file. I have to display them, and ...

  1. #1
    Registered User Cpro's Avatar
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    Array trouble

    Ok,
    I have a 2d array, and am reading the numbers from a file. I have to display them, and display the average of the sum of the columns and rows.
    I can display them, but i can't get the sum correct. It comes up with a wierd number.
    The part in bold is where i compute the sums of each row and column.
    Code:
    #include <iostream>
    #include <string>
    #include <cmath>
    #include <iomanip>
    #include <fstream>
    
    using namespace std;
    
    void Compute_Sums(int Array1[][3], int RowSums[], int Colsums[]);
    void Compute_Avg(int RowSums[], int Colsums[], float RowAvg[], float ColAvg[]);
    void Print(int RowSums[], int Colsums[], float RowAvg[], float ColAvg[]);
    
    void main()
    {
    	ifstream Array_Info;
    	Array_Info.open("A:IntFile.DAT");	
    
    	int Array1[7][3], RowSums[7], Colsums[3];
    	float RowAvg[7], ColAvg[3];
    
    	Compute_Sums(Array1, RowSums, Colsums);
    	Compute_Avg(RowSums, Colsums, RowAvg, ColAvg);
    	Print(RowSums, Colsums, RowAvg, ColAvg);
    	
    }
    
    void Compute_Sums(int Array1[][3], int RowSums[], int Colsums[])
    {
    	int row;
    	int column;
    	row = 0;
    	column = 0;
    		
    	for(column = 0; column < 3; column++)
    		Colsums[column] = 0;
    			
    	for(column = 0; column < 3; column++)
    		for(row = 0; row < 7; row++)
    			Colsums[column] = Colsums[column] + Array1[row][column];
    
    	for(row = 0; row < 7; row++)
    		RowSums[row] = 0;
    
    	for(row = 0; row < 7; row++)
    		for(column = 0; column < 3; column++)
    			RowSums[row] = RowSums[column] + Array1[row][column];
    		
    }
    void Compute_Avg(int RowSums[], int Colsums[], float RowAvg[], float ColAvg[])
    {
    	int row;
    	int column;
    	row = 0;
    	column = 0;
    
    	for(row=0; row<7; row++)
    		RowAvg[row]=RowSums[row]/3.0;
    	
    	for(column=0; column<3; column++)
    		ColAvg[column]=Colsums[column]/7.0;
    		
    }
    void Print(int RowSums[], int Colsums[], float RowAvg[], float ColAvg[])
    {
    	ifstream Array_Info;
    	Array_Info.open("A:IntFile.DAT");
    	int Array1[7][3];
    		
    	
    	cout<<"       "<<"Fish1"<<"  "<<"Fish2"<<"  "<<"Fish3"<<endl<<endl;
    	for(int row=0; row<7; row++)
    	{
    				
    		cout<<"lake "<<row+1;
    		for(int column=0; column<3; column++)
    		{
    			Array_Info>>Array1[row][column];
    			cout<<setw(6)<<Array1[row][column]<<' ';
    		}
    		cout<<endl;
    	}
    	cout<<endl<<Colsums[1]<<endl;
    }
    These are the numbers (not all are used, only 21).
    8 27 33 14 81 146 305
    249 412 71 226 4 144 55
    94 493 133 265 788 240
    380 117 88 25 60

    I output "Colsums[1]" to test to see if the sum was correct. It comes up with a wierd number.

  2. #2
    Registered User
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    >> reading the numbers from a file
    You are reading in the numbers during the Print function, which isn't called until after the sums are calculated.

  3. #3
    Registered User Cpro's Avatar
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    aww, i didn't even realize that. Thank you.

  4. #4
    and the hat of wrongness Salem's Avatar
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    > void main()
    *faints*
    If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut.
    If at first you don't succeed, try writing your phone number on the exam paper.
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  5. #5
    Frequently Quite Prolix dwks's Avatar
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    > void main()
    *faints*
    http://faq.cprogramming.com/cgi-bin/...&id=1043284376

    Was this intentional?
    Code:
    RowSums[row] = RowSums[column] + Array1[row][column];
    To avoid that kind of problem/ambiguity, you can write it like this:
    Code:
    RowSums[row] += Array1[row][column];
    You can do this at the variable's initialization:
    Code:
    int Colsums[3];
    
    	for(column = 0; column < 3; column++)
    		Colsums[column] = 0;
    ->
    Code:
    int Colsums[3] = {0, 0, 0};
    If you leave off elements, 0 is implied, so you could use
    Code:
    int Colsums[3] = {0};
    Or you could use memset (in <cstring>) instead of a for loop.

    I don't think you use anything from <string>, nor <cmath> for that matter.
    dwk

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