Write a C++ function to test whether a given 9x9 matrix contains a valid Sudoku

Question

Write a C++ function to test whether a given 9x9 matrix contains a valid Sudoku

configuration. The function should return 1 if the configuration is valid and 0 otherwise.

If you are not familiar with the rules of Sudoku, Wikipedia has a good summary:

http://en.wikipedia.org/wiki/Sudoku. The input matrix could be complete or

incomplete.

A complete matrix has all cells filled with numbers.

Notes:

- Only submit your source code (.cpp). This must be done on or before the due date

- Once again, no late submissions.

- Your program must include comments explaining your steps.

due Oct 30,2013

Explanation / Answer

int sudoku(int matrix[9][9])

{

int r, c, r1, c1, i;

int fill[9];

// check each row

for (r = 0; r < 9; r++)

{

// initialize fill to 0

for (i = 0; i < 9; i++)

fill[i] = 0;

// test each number in the row

for (c = 0; c < 9; c++)

{

int v = matrix[r][c];

if (v < 1 || v > 9 || fill[v-1] > 0)

return 0;

fill[v-1] = 1;

}

}

// check each column

for (c = 0; c < 9; c++)

{

for (i = 0; i < 9; i++)

fill[i] = 0;

for (r = 0; r < 9; r++)

{

int v = matrix[r][c];

if (v < 1 || v > 9 || fill[v-1] > 0)

return 0;

fill[v-1] = 1;

}

}

// check each box

r = c = 0;

while (r < 9)

{

for (i = 0; i < 9; i++)

fill[i] = 0;

for (r1 = 0; r1 < 3; r1++)

{

for (c1 = 0; c1 < 3; c1++)

{

int v = matrix[r+r1][c+c1];

if (v < 1 || v > 9 || fill[v-1] > 0)

return 0;

fill[v-1] = 1;

}

}

c += 3;

if (c >= 9)

{

c = 0;

r += 3;

}

}

return 1;

}

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