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  1. #include <iostream>
  2.  
  3. int main()
  4. {
  5.   int magicsq[3][3] = {0}; // initializes magic square with all 0s
  6.   // Algorithm of de la Loubere:
  7.   int row = 0, col = 1; // start coordinates
  8.   // assign start cell
  9.   magicsq[row][col] = 1;
  10.   for (int x = 2; x <= 9; ++x) {
  11.     // compute up-right coordinates
  12.     int rowT = row - 1; if (rowT < 0) rowT += 3;
  13.     int colT = col + 1; if (colT >= 3) colT -= 3;
  14.     // check whether cell not yet assigned
  15.     if (magicsq[rowT][colT]) {
  16.       // compute down coordinates
  17.       if (++row >= 3) row -= 3;
  18.     } else {
  19.       // use up-right coordinates
  20.       row = rowT; col = colT;
  21.     }
  22.     // assign next cell
  23.     magicsq[row][col] = x;
  24.   }
  25.   // output of result:
  26.   std::cout << "Magic Square:" << std::endl;
  27.   for (row = 0; row < 3; ++row) {
  28.     for (col = 0; col < 3; ++col) {
  29.       std::cout << ' ' << magicsq[row][col];
  30.     }
  31.     std::cout << std::endl;
  32.   }
  33.   // check result:
  34.   std::cout << "Row sums:";
  35.   for (row = 0; row < 3; ++row) {
  36.     int sum = 0;
  37.     for (col = 0; col < 3; ++col) sum += magicsq[row][col];
  38.     std::cout << ' ' << sum;
  39.   }
  40.   std::cout << std::endl;
  41.   std::cout << "Column sums:";
  42.   for (col = 0; col < 3; ++col) {
  43.     int sum = 0;
  44.     for (row = 0; row < 3; ++row) sum += magicsq[row][col];
  45.     std::cout << ' ' << sum;
  46.   }
  47.   std::cout << std::endl;
  48.   std::cout << "Diagonal sums: ";
  49.   int sumM = 0, sumC = 0;
  50.   for (row = 0; row < 3; ++row) {
  51.     sumM += magicsq[row][row];
  52.     sumC += magicsq[row][2 - row];
  53.   }
  54.   std::cout << ' ' << sumM << ' ' << sumC << std::endl;
  55.   // done
  56.   return 0;
  57. }
Success #stdin #stdout 0s 4460KB
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stdin
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Standard input is empty
stdout
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Magic Square:
 8 1 6
 3 5 7
 4 9 2
Row sums: 15 15 15
Column sums: 15 15 15
Diagonal sums:  15 15
https://ideone.com/sMJKoz
language:
C++ (gcc 8.3)
created:
7 years ago
visibility:
public

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