Question

c++ PROGRAM to write a spiral matrix? can any one give the code?

Answer 1

#include<stdio.h>


int main()
{
int i,j,m,n,a[100][100];
int p=1,q=1,r=2;
scanf("%d",&n);
scanf("%d",&m);



for (i=1;i<=m;i++)
{ for (j=1;j<=n;j++)
{scanf("%d ",a[i][j]);}

}
while (m>=1 && n>=1)
{for(j=p;j<=n;j++)
{
i=q;
printf("%d ",a[i][j]);
}
for(i=r;i<=m;i++)
{
j=n;
printf("%d ",a[i][j]);
}
for(j=n-1;j>=p;j--)
{
i=m;
printf("%d ",a[i][j]);
}
for(i=m-1;i>p;i--)
{
j=q;
printf("%d ",a[i][j]);
}
m=m-1;
n=n-1;
p++;
q++;
r++;
}

return 0;
}
code written so far

Answer 2

why don't we start off writing this code for a smaller matrix and add some code to fill in the values automatically?

Answer 3

so do you want to fill in a matrix in spiral form, or just print it in spiral form? because your code fills in the matrix normally, then tries to print it in spiral order.

Answer 4

```
#include<stdio.h>


int main()
{
int i,j,m,n,a[10][10];
int p=1,q=1,r=2;
scanf("%d",&n);
scanf("%d",&m);



for (i=1;i<=m;i++)
{
for (j=1;j<=n;j++)
{scanf("%d ",a[i][j]);}
}

while (m>=1 && n>=1)
{
for(j=p;j<=n;j++)
{
i=q;
printf("%d ",a[i][j]);
}
for(i=r;i<=m;i++)
{
j=n;
printf("%d ",a[i][j]);
}
for(j=n-1;j>=p;j--)
{
i=m;
printf("%d ",a[i][j]);
}
for(i=m-1;i>p;i--)
{
j=q;
printf("%d ",a[i][j]);
}
m=m-1;
n=n-1;
p++;
q++;
r++;
}

return 0;
}
```
I have rewritten your code to be more legible

Answer 5

thanks :)

Answer 6

yeah i want it printed in spiral order
the matrix is given by the user

Answer 7

there is always the same error being dispalyed, but i cant figure out... whats wrong

Answer 8

well for now let's run a test matrix that just inputs the numbers 1-16, like
```
int main(void)
{
int i,j,m,n,a[4][4];

\\ rest of code

int x=1;
for (i=1;i<=m;i++)
{
for (j=1;j<=n;j++)
{
a[i][j] = x;
x++;
}
}
```
or something so we have a control stub, let me compile it and see what I get, one sec..

Answer 9

btw to type code, enclose it in backticks like so:
(```)
code
(```)

remove the parentheses

Answer 10

the error you were getting was on the scanf line? invalid argument type 'int' instead of int * ?

Answer 11

canu u give an example i did not quite understand, sorry

Answer 12

i'm saying, your program creates a 100x100 matrix and then asks the user to scan in each of the 10000 numbers, which is a bad test case
hence, let's work with a 4x4 matrix that we fill with the numbers 1,2,3,....,16 automatically, so we can debug it more easily

Answer 13

yeah thats the error! I am new to programming I don't understand what is that supposed to mean, sure I will use smaller matrix. thanks
How am I supposed to remove the error

Answer 14

since the error says you need to input type int*, you should be using the "address of" operator in that line, &

Answer 15

a[i][j] is a particular integer, &a[i][j] is the address of that location in memory. scanf needs to know where you are storing things in memory to take in values for variable from the user, so the & operator is required before the variable

Answer 16

omg! it shud be scanf("%d",&a[i][j])..... I was so exhausted after thinking and writing this that my brain stopped working.
Thankyou very much

Answer 17

welcome, let me know if you have anymore trouble

Answer 18

no prob I am getting the write output for a 3 X 4 matrix. Thank you again

Answer 19

cool, welcome again :)

Answer 20

now i need to do the next problem
Write a program that reads an NxN square matrix M that calculates the sum of the elements in individual rows, individual columns and the two main diagonals. Among these sums, print the largest.

Consider the following matrix of order 3x3:

1 10 13
2 14 12
3 9 8

The row sum values are 1+10+13=24, 2+14+12=28 and 3+9+8=20. The column sum values are 1+2+3=6, 10+14+9=33 and 13+12+8=33. The diagonal sums are 1+14+8=23 and 13+14+3=30. The expected output is maximum among these sums, which is 33.
THANKS ahain :D