Is Sudoku Valid

Given an incomplete Sudoku configuration in terms of a 9x9 2-D square matrix(mat[][]) the task to check if the current configuration is valid or not where a 0 represents an empty block.

Note: Current valid configuration does not ensure validity of the final solved sudoku.

• Time : O(n^2)
• Space : O(1)

class Solution{
    int rows[9];
    int cells[9];
    int cols[9];
public:
    int isValid(vector<vector<int>> mat){
        memset(rows, 0, sizeof rows);
        memset(cells, 0, sizeof cells);
        memset(cols, 0, sizeof cols);

        for(int i = 0; i < 9; i++) {
            for(int j = 0; j < 9; j++) {
                if(!mat[i][j]) continue;
                int row = i, col = j, cell = (i / 3) * 3 + (j / 3);
                if(rows[row] & (1<<mat[i][j])) return false;
                if(cols[col] & (1<<mat[i][j])) return false;
                if(cells[cell] & (1<<mat[i][j])) return false;
                rows[row] |= 1<<mat[i][j];
                cols[col] |= 1<<mat[i][j];
                cells[cell] |= 1<<mat[i][j];
            }
        }
        return true;
    }
};