help about 2D ARRAY...

This is a discussion on help about 2D ARRAY... within the C Programming forums, part of the General Programming Boards category; i want to ask.. how to create 2D array by asking the user the value.... TQVM.....

  1. #1
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    Question help about 2D ARRAY...

    i want to ask..
    how to create 2D array by asking the user the value....


    TQVM..

  2. #2
    spurious conceit MK27's Avatar
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    Code:
    #include <stdio.h>
    #include <stdlib.h>
    
    int *getrow(int length) {
    	int i, ii, ch, *row=malloc(length*sizeof(int));
    	char buffer[16];
    	
    	printf("Enter %d numbers seperated by commas\n"
    		"(max 4 digits): ", length);
    	for (i=0; i<length; i++) {
    		ii=0;
    		while ((ch=fgetc(stdin))!=',') {
    			if (ch=='\n') break;
    			buffer[ii]=ch; 	
    			ii++;
    		}
    		buffer[ii]='\0';
    		row[i]=atoi(buffer);
    	}
    	return row;
    }	
    
    void showmatrix (int *matrix[], int rows, int cols) {
    	int i, ii;
    	for (i=0; i<rows; i++) {
    		for (ii=0; ii<cols; ii++) printf("%5d", matrix[i][ii]);
    		printf("\n");
    	}
    }
    	
    
    int main(int argc, char *argv[]) {
    	int rows, cols, i, **matrix;
    	if (argc<3) {
    		printf("Usage \"%s [NO OF ROWS][NO OF COLS]\", eg %s 3 3\n",argv[0],argv[0]);
    		return 0;
    	}
    	
    	rows=atoi(argv[1]); cols=atoi(argv[2]);
    	matrix=malloc(rows*sizeof(int*));
    	for (i=0; i<rows; i++) {
    /* LEAK:	matrix[i]=malloc(cols*sizeof(int));   */
    		matrix[i]=getrow(cols);
    	}
    	showmatrix(matrix,rows,cols);
    	for (i=0; i<rows; i++) free(matrix[i]);
            free(matrix);
    	return 0;
    }
    Output:
    Code:
    [/root/C] ./a.out 2 4
    Enter 4 numbers seperated by commas
    (max 4 digits): 999,-128, 9,  666
    Enter 4 numbers seperated by commas
    (max 4 digits): 1024, 42, 0, 11
      999 -128    9  666
     1024   42    0   11
    Last edited by MK27; 02-27-2009 at 08:48 AM.
    C programming resources:
    GNU C Function and Macro Index -- glibc reference manual
    The C Book -- nice online learner guide
    Current ISO draft standard
    CCAN -- new CPAN like open source library repository
    3 (different) GNU debugger tutorials: #1 -- #2 -- #3
    cpwiki -- our wiki on sourceforge

  3. #3
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    Quote Originally Posted by MK27 View Post
    Code:
    #include <stdio.h>
    #include <stdlib.h>
    
    int *getrow(int length) {
    	int i, ii, ch, *row=malloc(length*sizeof(int));
    
    }
    	
    
    	for (i=0; i<rows; i++) {
    		matrix[i]=malloc(cols*sizeof(int));	
    	                matrix[i]=getrow(cols);
    	}
    matrix[i]=malloc(cols*sizeof(int));
    line is not required as memory has been allocated twice (second time in getrow). Which will result in memory leak

  4. #4
    spurious conceit MK27's Avatar
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    Quote Originally Posted by ashu0204 View Post
    matrix[i]=malloc(cols*sizeof(int));
    line is not required as memory has been allocated twice (second time in getrow). Which will result in memory leak
    Good catch -- I'll remove that from the post, for what it's worth. I also forgot to free(matrix) after freeing the rows...
    Last edited by MK27; 02-27-2009 at 08:45 AM.
    C programming resources:
    GNU C Function and Macro Index -- glibc reference manual
    The C Book -- nice online learner guide
    Current ISO draft standard
    CCAN -- new CPAN like open source library repository
    3 (different) GNU debugger tutorials: #1 -- #2 -- #3
    cpwiki -- our wiki on sourceforge

  5. #5
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    A C array is very simple, you can ask the user:
    Code:
    int value;
    int array2d[10][5];
    for(int k = 0; k < 10; k++){
      for(int i = 0; i < 5; i++){
        cout << "What is value for index i " << i << " inside the array k " << k << "?" << endl;
        cin << value;
        array2d[k][i] = value;
      }
    }
    Easy isn't it?
    ★ Inferno provides Programming Tutorials in a variety of languages. Join our Programming Forums. ★

  6. #6
    C++ Witch laserlight's Avatar
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    execute's example is good if your 2D array is of a fixed size, but you would need to convert the example from using the C++ version of the standard input stream to the C version.

    On the other hand, it seems that previous responses interpreted "how to create 2D array by asking the user the value" as "how to create 2D array after getting the dimensions from the user".
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