Thread: What is wrong with the code? How the element values of array changes?

  1. #1
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    Exclamation What is wrong with the code? How the element values of array changes?

    Code:
    #include <stdio.h>
    
    int main()
    {
    	int i,j,row=1,col=3,sum=0;
    	int a[row][col];
    	printf("Enter the elements on by one:");
    	for(i=1;i<=row;i++)
    	{
    		for(j=1;j<=col;j++)
    		{
    			scanf("%d",&a[i][j]);						
    		}
    	}
    	
    	printf("The A matrix \n");
    	for(i=1;i<=row;i++)
    	{
    		for(j=1;j<=col;j++)
    		{
    			printf("%5d",a[i][j]);			
    		}
    		printf("\n");
    	}
    	int colsum[col];	//To calculate column sum
    	for(j=1;j<=col;j++)
    	{
    		colsum[j]=0;
    		for(i=1;i<=row;i++)
    		{
    			colsum[j] = colsum[j] + a[i][j];
    		}
    	}
    	printf("The A matrix \n");
    	for(i=1;i<=row;i++)
    	{
    		for(j=1;j<=col;j++)
    		{
    			printf("%5d",a[i][j]);			
    		}
    		printf("\n");
    	}
    	printf("\n The Column Sum is =");
    	for(i=1;i<=col;i++)
    		{
    			printf("%5d",colsum[i]);			
    		}
    	return(0);
    }

  2. #2
    and the hat of int overfl Salem's Avatar
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    > for(i=1;i<=row;i++)
    > for(j=1;j<=col;j++)
    Arrays start at subscript 0, not 1.

    for ( i = 0 ; i < N ; i++ )
    is the idiomatic loop for iterating over an array of length N.
    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.

  3. #3
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    Agreed, subscript start at 0, but starting at 1 is not invalid.

  4. #4
    C++ Witch laserlight's Avatar
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    Agreed, subscript start at 0, but starting at 1 is not invalid.
    True, if you don't ever want to use the element at index 0. On the other hand, accessing a[row][col] when you declared a as int a[row][col] is invalid as you're accessing the array out of bounds.

    So you either want to start from 0, or you want to declare a as int a[row + 1][col + 1].
    Quote Originally Posted by Bjarne Stroustrup (2000-10-14)
    I get maybe two dozen requests for help with some sort of programming or design problem every day. Most have more sense than to send me hundreds of lines of code. If they do, I ask them to find the smallest example that exhibits the problem and send me that. Mostly, they then find the error themselves. "Finding the smallest program that demonstrates the error" is a powerful debugging tool.
    Look up a C++ Reference and learn How To Ask Questions The Smart Way

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