howto build this addition matrix

This is a discussion on howto build this addition matrix within the C Programming forums, part of the General Programming Boards category; this matrix 0 2 2 4 0 2 2 1 8 6 0 3 should return the sum of 224+221+8603 ...

  1. #1
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    howto build this addition matrix

    this matrix
    0 2 2 4
    0 2 2 1
    8 6 0 3

    should return the sum of 224+221+8603
    this is a part of a code
    why its not working??
    Code:
    int power=1;
    int coef=0;
    for (index = 0; index < rows; index++)
       {
          for (kndex = 0; kndex < cols; kndex++)
          {
              for (z=0;z<(cols-kndex);z++){
                  pwer=pwer*10;
              }
                coef=matrix[index][kndex]*pwer;
    
                tsum=tsum+coef;
             }
    
       }
       printf("%d ",tsum);
    Last edited by transgalactic2; 12-23-2008 at 05:12 PM.

  2. #2
    Registered User carrotcake1029's Avatar
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    You should spread it out and make it easier to understand. I find myself getting lost in embedded loops all the time. If you want, you can use this method:

    Code:
    #include <stdio.h>
    
    int main (void)
    {
    	int matrix[] = {0, 2, 2, 4, 0, 2, 2, 1, 8, 6, 0, 3};
    	int i, j, sum = 0;
    	
    	for (i = 0; i < 12; i++)
    	{
    		switch (i % 4)
    		{
    			case 0:
    				sum += matrix[i] * 1000;
    				break;
    			case 1:
    				sum += matrix[i] * 100;
    				break;
    			case 2:
    				sum += matrix[i] * 10;
    				break;
    			case 3:
    				sum += matrix[i] * 1;
    				break;
    		}
    			
    	}
    	
    	printf("%d\n", sum);		
    		
    	return 0;
    }

  3. #3
    and the Hat of Guessing tabstop's Avatar
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    It's not working because your algorithm (at least as implemented) is horribly, horribly broken. I can't tell whether what you're trying to do is correct and you've just flubbed the algorithm, or your algorithm was wrong to start with. So trace through it, already (C is not a write-only language!) and see if it's doing what you expect.

  4. #4
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    Quote Originally Posted by transgalactic2 View Post
    this matrix
    0 2 2 4
    0 2 2 1
    8 6 0 3

    should return the sum of 224+221+8603
    this is a part of a code
    why its not working??
    Code:
    int power=1;
    int coef=0;
    for (index = 0; index < rows; index++)
       {
          for (kndex = 0; kndex < cols; kndex++)
          {
              for (z=0;z<(cols-kndex);z++){
                  pwer=pwer*10;
              }
                coef=matrix[index][kndex]*pwer;
    
                tsum=tsum+coef;
             }
    
       }
       printf("%d ",tsum);
    1) power is misspelled or never used
    2) pwer needs to be reset to 1 after the tsum=tsum+coef, line of code
    3) z in the for loop, needs to start at 1, not zero.

    Your algorithm is fine, just a few mistakes. Here's a corrected version:

    Code:
    #include <stdio.h>
    #define rows 3
    #define cols 3
    
    int main()  {
       int index, kndex, z, pwer, tsum, coef;
    
       int matrix[rows][cols] = {
       { 3, 5, 5 },      //355
       { 1, 2, 5 },      //125
       { 4, 5, 6 } };    //456
       //======================
       //                  936
    
    tsum = coef = 0;
    pwer = 1; 
    for (index = 0; index < rows; index++)
       {
          for (kndex = 0; kndex < cols; kndex++)
          {
              for (z=1;z<(cols-kndex);z++){
                  pwer=pwer*10;
              }
                coef=matrix[index][kndex]*pwer;
    
                tsum=tsum+coef;
                pwer = 1;
             }
    
       }
       printf("%d ",tsum);
       tsum  = getchar();
       return 0;
    }

  5. #5
    Woof, woof! zacs7's Avatar
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    Australia
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    Ew calculating the powers of 10 for every column seems a bit wasteful...

    Code:
       for(row = 0; row < ROWS; row++)
       {
          power = 1;
    
          for(col = COLS - 1; col >= 0; col--)
          {
             coeff += matrix[row][col] * power;
             power *= 10;
          }
    
          printf("%d\n", coeff);
       }
    Is MUCH nicer. You could even make it faster by pre-calculating the powers of 10.

    Also try not to strip the vowels out of your variable names, ie "pwer" is a terrible name for "power".

  6. #6
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    thanks

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