Magic Square

[RoastChicken]

Hello, i am new in this forum as you can see, i hope someone can help me out with this little problem, i have coded a magic square program in c++, it is working 90%.
The magic square is 4x4 and only accepts numbers between 1 and 16.
What is failing here is that it cannot accept repeated numbers. I cannot overcome this problem, and i am running out of ideas i hope someone can help me out and explain to me what i need to do.

The programa detects if the number has been already inserted or not, and it prompts the user for a different number, but when prompt to enter a different number if the user inserts another number that has already been inserted before the program accepts it and continues.

Thanks in advance for your help.

PS: The couts was written originally in Portuguese, i have translated the couts and comments.

#include <iostream>

using namespace std;
 
int main() {
	int magic[4][4]={0};
    int cont=1, lin, col, lin1=0, col1=0, linesum=0, columnsum=0, inicialsum=0, ismagic=1, diagonalsum1=0, diagonalsum2=0;

    //preenche o quadrado mágico
    cout << "Fill your magic square!!" << endl;

    for(lin=0;lin<4;lin++) {
		for(col=0;col<4;col++) {
			cout << ":::: Magic Square only accepts values between 1 and 16::::" << endl;
			do {
				cout << "Insert value for line " << lin+1 << " :: Column " << col+1 << ": " << endl;
				cin >> magic[lin][col];
				if(lin+col>0) {
					for(lin1=3; lin1>=0;lin1--) {
						for(col1=3;col1>=0;col1--){
							if(magic[lin1][col1] == magic[lin][col] && lin1+col1 != lin+col) {
								cout << "This has been added already!";
								cout << "Please insert a different number: ";
								cin >> magic[lin][col];
							}
						}
					}
				}
			}while(magic[lin][col] <1 || magic[lin][col] >16);
			
		}
	}

    //sum of 1st column

	for(lin=0;lin<4;lin++) {
		inicialsum+=magic[lin][0];
	}

    //sum of all column

    for(col=0;col<4;col++) {
		columnsum=0;
		for(lin=0;lin<4;lin++) {
			columnsum+=magic[lin][0];
		}
		if(columnsum != inicialsum)
			ismagic=0;
	}
	cout << "sum of columns = " << columnsum << endl;
    //line sum

    for(lin=0;lin<4;lin++) {
		linesum=0;
		for(col=0;col<4;col++) {
			linesum+=magic[lin][col];
		}
		if(linesum != inicialsum)
			ismagic=0;
	}
	cout << "sum if lines = " << linesum << endl;

    //sum of 1st diagonal

    for(lin=0;lin<4;lin++) {
		for(col=0;col<4;col++) {
			if(lin==col) {
				diagonalsum1+=magic[lin][col];
			}
		}
	}
		if(diagonalsum1 != inicialsum)
			ismagic=0;
	cout << "sum of 1st diagonal = " << diagonalsum1 << endl;

    //sum of 2nd diagonal
	col=4;
	for(lin=0;lin<4;lin++) {
		col--;
		diagonalsum2+=magic[lin][col];
	}
	if(diagonalsum2 != inicialsum)
		ismagic=0;
	cout << "sum of 2nd diagonal = " << diagonalsum2 << endl;
	 

    if(ismagic==1)
		cout << "Great! It is a magic square" << endl;
	else
		cout << "Not a magic square" << endl;
	system("pause");
	return 0;
}

[giblit]

Put all the previous values in a vector then when you try to.input new value compare with the vector

[RoastChicken]

Hi, thank you for your answer. I'm not sure if i got your answer right, but here's what i have done.

Now it only checks twice for repeated numbers, but after the 2nd check, i can input the same value again.

Thank you for your help in advance

    for(lin=0;lin<4;lin++) {
		for(col=0;col<4;col++) {
			cout << ":::: Magic Square only accepts values between 1 and 16 ::::" << endl;
			do {
				cout << "Enter the value for line " << lin+1 << " :: clumn " << col+1 << ": " << endl;
				cin >> magic[lin][col];
				if(lin+col>0) {
					for(lin1=3; lin1>=0;lin1--) {
						for(col1=3;col1>=0;col1--){
							if(magic[lin1][col1] == magic[lin][col] && lin1+col1 != lin+col) {
								cout << "Please enter a different number: ";
								cin >> magic[lin][col];
								magic1[0][0] = magic[lin][col];
								for(lin1=3; lin1>=0;lin1--) {
									for(col1=3;col1>=0;col1--){
										if(magic1[0][0] == magic[lin][col]) {
											cout << "Please enter a different number: ";
											cin >> magic[lin][col];
										}
									}
								}

							}
						}
					}
				}
			}while(magic[lin][col] <1 || magic[lin][col] >16);
		}
	}

[RoastChicken]

I am sorry, i'm sure i didn't got your answer right. Anyone can help me out please?

[Chervil]

Using a vector:

    vector<int> accepted;
    int n;

    cout << ":::: Magic Square only accepts values between 1 and 16 ::::" << endl;

    for (lin=0; lin<4; lin++)
    {
        for (col=0; col<4; col++)
        {
            do {
                cout << "Enter the value for line " << lin+1 << " :: column " << col+1 << ": " << endl;
                cin >> n;
                bool found;

                do {
                    found = false;
                    for (int i=0; i<accepted.size(); i++)
                    {
                        if (accepted[i] == n)
                        {
                            found = true;
                            break;
                        }
                    }

                    if (found)
                    {
                        cout << "Please enter a different number: ";
                        cin >> n;
                    }
                } while (found);

                magic[lin][col] = n;
                accepted.push_back(n);
            } while (magic[lin][col] < 1 || magic[lin][col] > 16);
        }
    }

[keskiverto]

std::set<int> myset;
// looking for numbers in [1..Max]
..
int value;
bool waiting = true;
while ( waiting && std::cin >> value )
 {
  if ( value < 1 || Max < value ) // error: not in range
  else if ( 0 != myset.count( value ) // error: already used
  else // good new value
    {
      myset.insert( value ); // store for the check
      magic1[line][col] = value; // put into square
      waiting = false;
    }
 }
..

[Chervil]

@keskiverto set is a good solution :)

[RoastChicken]

Thanks guys! Will try that out. Cheers