#include #include #include #include #include using namespace std; namespace { constexpr int Size{9}; // Display Sudoku auto print = [](auto&& sudoku) { for(auto r = 0; r < Size; r++){ for(auto c = 0; c < Size; c++){ int d{sudoku[r *Size + c]}; cout << (d ? static_cast(d+48) : '-') << " "; } cout << '\n'; }}; using Ints = valarray; using Mst = multiset; } auto mark_err = [](auto&& eMarks, auto&& sel,auto&& ws) { // add the current working set (row, // col or grid) in the set to find out // count of each digit Mst mst(begin(ws), end(ws)); Ints tmp = eMarks[sel]; // select the target (row, col or grid) // according to the current working set for(auto e:ws) if(mst.count(e)>1) for(int i{0}; i < Size; i++) if (e == ws[i]) tmp[i] = e; // update error marks. It is updated in // order of rows, cols and grid eMarks[sel] = tmp; }; // check if sudoku is valid or not. If not // valid, mark the error locations. auto check_sudoku = [](auto&& Sample, auto&& eMarks) { // indices for 3*3 square selection valarrayidx{0,1,2,9,10,11,18,19,20}; for(int i{0}; i < Size;) { slice rs(i * Size, Size, 1),//row slice cs(i,Size,Size); //col slice // mark errors if any in the order // rows, cols and grid mark_err(eMarks, rs, Ints(Sample[rs])); mark_err(eMarks, cs, Ints(Sample[cs])); mark_err(eMarks,idx,Ints(Sample[idx])); idx += 3; ++i; if(!(i % 3)) idx += 2 * Size; } return eMarks.sum() == 0; }; int main(){ vector Samples{ {1,2,3,4,5,7,7,8,9, 2,3,4,5,6,7,8,9,1, 5,6,7,8,9,1,2,3,4, 6,7,8,9,1,2,3,4,5, 9,1,2,3,4,5,6,7,8, 3,4,5,6,7,8,9,1,2, 4,5,6,7,8,9,1,2,3, 7,8,9,1,2,3,4,5,6, 8,9,1,2,3,4,5,6,7}, {3,5,2,9,1,8,6,7,4, 8,9,7,2,4,6,5,1,3, 6,4,1,7,5,3,2,8,9, 7,8,3,5,6,9,4,2,1, 9,2,6,1,3,4,7,5,8, 4,1,5,8,2,7,9,3,6, 1,6,4,3,7,5,8,9,2, 2,7,8,4,9,1,3,6,5, 5,3,9,6,8,2,1,4,7}}; for(auto const& sample : Samples) { // will show error locations if any Ints eMarks(0,Size*Size); print(sample); bool isValid{check_sudoku( sample,eMarks)}; cout << (isValid ? "valid\n\n" : "invalid\n\n"); if(!isValid){ // display error locations only if // Sudoku is not valid cout << "Error Locations:\n"; print(eMarks); cout << "\n\n"; } } }

[Challenge] Sudoku_Validator_with_Error_Locations.cpp