reading arrays?

This is a discussion on reading arrays? within the C Programming forums, part of the General Programming Boards category; hello, I'm new to C and have a pretty basic question. I have a 4 x 5 matrix saved in ...

  1. #1
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    reading arrays?

    hello, I'm new to C and have a pretty basic question. I have a 4 x 5 matrix saved in as a txt file and I can't figure out how to make my program stop reading the input file. I want the input to be stored in an array. I think there must be a way to do this by putting a while loop as the outer loop of my program but I'm not sure what condition to put in the loop.

    this is my code:


    Code:
    #include <stdio.h>
    #include <stdlib.h>
    
    
    FILE *fin, *fout;
    
    main() {
           
           
           int A [4] [5] ;
           int r = 0;
           int c = 0;
           int r_max = 4;
           int c_max = 5;
           int i;
           	
    
                    fin = fopen("matrix.txt", "r");	  
                    fout = fopen("output.txt", "w");
    	 
                   
       
                   	for(i = 0; r < r_max; i++) {
    	for(j = 0; c < c_max; j++) {
    	
                    fscanf(fin, "%d", &A[i][j]);
    	fprintf(fout, "%d ", A[i][j]);
    	}
    	fprintf(fout, "\n");
    		}
    but it just reads the input file forever and crashes, any help with this would be greatly appreciated, thank you.

  2. #2
    cwr
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    Look at your for loops.. you are incrementing i, but checking the value of r. Inside, you are incrementing j, but checking the value of c, that doesn't make sense.

  3. #3
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    Sep 2005
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    ahhh true, thank you, i didn't notice that, i changed that in my code and also added a while loop, but my output is still going on forever, instead of stopping after reading the matrix, any idea why? here's my revised code. Thank you

    Code:
    #include <stdio.h>
    #include <stdlib.h>
    
    
    FILE *fin, *fout;
    
    main() {
           
           
           int A [3] [4] ;
           int r = 0;
           int c = 0;
           int r_max = 4;
           int c_max = 5;
           int i;
           int j;
           int k;
    
                    fin = fopen("matrix.txt", "r");	  
                    fout = fopen("output.txt", "w");
    	 
                   
       
      	while(fscanf(fin, "%d", &k)  != EOF ) {
          
        for(r = 0; r < r_max; r++) {
    	for(c = 0; c < c_max; c++) {
    	
        fscanf(fin, "%d", &A[i][j]);
    	fprintf(fout, "%d ", A[i][j]);
    	}
    	fprintf(fout, "\n");
    		}
    
          printf("%d",A[2][2]);
          
          getchar();
          
           }
    }

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