The best performance improvement is the transition from the nonworking state to the working state. John Ousterhout
The eight queen’s puzzle is the problem of placing eight chess queens on an 8 x 8 chessboard so that no two queens threaten each other. Thus, a solution requires that no two queens share the same row, column, or diagonal.
Backtracking eliminates or avoids the partial candidate solutions as soon as it finds that that path cannot lead to a solution. We are given 4 x 4 chessboard and we need to place 4 queens in non-attacking places on this board.
Solution for 4 Queen Problem * Q * * * * * Q Q * * * * * Q * * * Q * Q * * * * * * Q * Q * *