wrong output for simple program

Question

I started to code a really simple task but I keep getting the wrong output. Help me, I'm desperate! The problem is: I have to print a table 4*10. The numbers in the table go from 1 to 40 and they are ascending- the table looks like this:

1 2 3 4 5 6 7 8 9 10
11 12 13 14 15 16 17 18 19 20
21 22 23 24 25 26 27 28 29 30
31 32 33 34 35 36 37 38 39 40

My task is to replace the every other multiple of 3 ( 3, 9, 15) is by the number 2. Every multiple of 5 that hasn't already been used is replaced by the number 3. Everything else is replaced by 1.

 #include<cstdio>
#include<cstring>


using namespace std;

    int table[10][4];
    int i,j;
    int br;

int main()
{
    br=1;


    for(i=0;i<4;i++)
    for(j=0;j<10;j++)
    {

    if(br%6==3) table[i][j]=2;
    else if(br%5==0 && br%6!=3) table[i][j]=3;
    else table[i][j]=1;


    br++;
    }


    for(i=0;i<4;i++)
    {for(j=0;j<10;j++)
    {
    printf("%d",table[i][j]);
    }
    printf("\n");
    }



return 0;
}

The output I keep getting :
1121111121
1111211111
2111112131
1121311123

The output I should get:
1121311123
1111211113
2111312113
1121311123

Enable all warnings and debugging options (e.g. compile with g++ -Wall -g) and use the debugger (e.g. gdb) — Basile Starynkevitch
– Basile Starynkevitch, Commented Dec 14, 2013 at 20:16
anyway, note that the table-ness is a property of the presentation only, and that your logic only needs to deal with the sequence of consecutive integers starting with 1 and ending with 40. — Cheers and hth. - Alf
– Cheers and hth. - Alf, Commented Dec 14, 2013 at 20:19
For example, 15 is replaced by 2 (it is a multiple of 3), and therefore should not be replaced by 3, although it is the multiple of 5. — user2166248
– user2166248, Commented Dec 14, 2013 at 20:20

Jeremy Friesner · Accepted Answer · 2013-12-14 20:22:16Z

1

One problem is that you are using your indices backwards with respect to how you declared your array:

int table[10][4];

for(i=0;i<4;i++)
for(j=0;j<10;j++)
{
   if(br%6==3) table[i][j]=2;
   else if(br%5==0 && br%6!=3) table[i][j]=3;
   else table[i][j]=1;

See how your (i) variable in the for loop is set to go 0,1,2,3 and your (j) variable in the inner loop is set to go (0,1,2,3,...,9) ? Then you set items in your array using table[i][j], which means that you'll be setting table[0][0] through table[3][9], but your table is declared as table[10][4].

The solution would be either to change your table declaration to be table[4][10], or alternatively change your instances of table[i][j] to be table[j][i] instead. Either way will work, as long as your for-loop ranges match your table's dimensions.

answered Dec 14, 2013 at 20:22

Jeremy Friesner

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Comments

leemes · Accepted Answer · 2013-12-14 20:21:55Z

1

You access the array in the wrong order. Instead of

table[i][j];

you should write

table[j][i];

whenever accessing your table as i denotes your row and j your column (as long as you name them consistently).

Alternatively swap the indexing in the table declaration, i.e.

int table[4][10];

instead of

int table[10][4];

The output is then correct.

answered Dec 14, 2013 at 20:21

leemes

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1 Comment

Hossein Over a year ago

Or simply define the array as int table[4][10]; instead.

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