Finding Duplicate value in 2d array 3x3 magic Square - c

Question

Im trying to create a 2D array 3x3 square.
Calculation and checking for it is done.
Right now, am trying to prevent repeated numbers from happening in the 2d array.
I tried using a for loop to brute force but cygwin compiles gives me error
Below is my code.
How do i go about checking 2d array?
#include <stdio.h> /* printf */
/*Preprocessor*/
/*set N constant 3*/
#define N 3
typedef enum {false,true}
bool;
int main()
{
/*initialize size to 3*/
int size =3;
int sum, sum1, sum2,array[N][N];
int row, col = 0;
int i, j, duplicate =0;
/* variable to
indicate process reached*/
int checkf =0;
/*input into the array of an array*/
for(row =0; row <size; row++)
{
for(col =0; col < size; col++)
{
scanf("%d", &array[row][col]);
}
}
**/*check for repeated values*/
for(row =0; row<9; row++)
{
for(col=0; col <9; col++)
{
if(array==array[row][col])
}
}**
/*Diagonal*/
/*sum of diagonal from the left
equals to sum of diagonal
from the right */
/*initialize sum2 to 0*/
sum2 =0;
/*check if row less than 3*/
for(row=0; row< size; row++)
{
/*check if col less than 3*/
for(col=0;col<size; col++)
{
/*number of row
equals number of col*/
if(row == col)
{
/*addition*/
sum2 = sum2 + array[row][col];
}
}
}
/*row*/
/*check if row less than 3*/
for(row=0; row < size; row++)
{
/*initialize sum */
sum = 0;
/*check if col less than 3*/
for(col=0; col <size; col++)
{
/*addition of numbers*/
sum = sum + array[row][col];
}
/*check if all additions
adds up to same sum*/
if(sum2 == sum)
{
/*a flag or check to print*/
checkf =1;
}
else
{
/*a flag or check to print*/
checkf =0;
break;
}
}
/*Columns*/
/*check if row less than 3*/
for(row = 0; row < size; row++)
{
/*initialize sum */
sum1 =0;
/*check if col less than 3*/
for(col = 0; col < size; col++)
{
/*addition*/
sum1 = sum1 + array[col][row];
}
/*sum of diagonal equals
sum of columns*/
if(sum == sum1)
{
/*a flag or check to print*/
checkf =1;
}
else
{
/*a flag or check to print*/
checkf =0;
break;
}
}
/*if statement is true
prints and display*/
if(checkf ==1)
{
printf("This is a magic square.\n");
}
else
{
/*print and display*/
printf("This is not a magic square.\n");
}
return 0;
}

Answer 1

If you had a flat, one-dimensional array (of fixed size N, say), you would check all elements against every element to its left:
int unique1d(int array[N])
{
int i, j;
for(i = 1; i < N*N; i++) {
for(j = 0; j < i; j++) {
if (array[i] == array[j]) return 0;
}
}
return 1;
}
You can do the same for a two-dimensional array, when you "flatten" the indices first. Say you enumerate the cells of your 3×3 grid with "flat" indices like so:
0 1 2
3 4 5
6 7 8
Then you get:
flat = row * N + col;
and, conversely:
row = flat / N; // truncating int division gives row
col = flat % N; // remainder gives column
So a function that tests whether there are duplicates in your N×N grid would look like this:
int unique(int array[N][N])
{
int i, j;
for(i = 1; i < N*N; i++) {
for(j = 0; j < i; j++) {
if (array[i / 3][i % 3] == array[j / 3][j % 3]) return 0;
}
}
return 1;
}
I've made that into a separate function, because it makes the code clearer. Not how you don't need a separate flag and a break. You can return the result explicitly as soon as you have found it. (Also, the break would have to break out of a nested loop, but the break keyword in C just jumps out of the inner loop.)
(The rest of your code that checks whether the square is magic or not looks a bit suspicious, too. For example, you should start with the assumption that the square is magic and then set your flag to false if one of the conditions for a magic square doesn't hold. You never have to set that flag back to true again. But that's a topic for another question.)
Edit: In order to explain the function better, here's example client code. This is essentially your program without the magic check. N must be a defined constant, as it is in your program.
int main()
{
int array[N][N];
int row, col;
for(row =0; row < N; row++) {
for(col =0; col < N; col++) {
scanf("%d", &array[row][col]);
}
}
if (unique(array)) {
puts("Values are unique");
} else {
puts("There are duplicate values.");
}
return 0;
}