This is one possible solution for the 4-queens problem. That is, we get the solution (2, 4, 1, 3). Then we have to backtrack till 'q 1' and place it to (1, 2) and then all other queens are placed safely by moving q 2 to (2, 4), q 3 to (3, 1) and q 4 to (4, 3). But later this position also leads to a dead end, and no place is found where 'q 4' can be placed safely.

Then we obtain the position for placing 'q 3' which is (3, 2). So we backtrack one step and place the queen 'q 2' in (2, 4), the next best possible solution. (2, 3) but then no position is left for placing queen 'q 3' safely. Thus the first acceptable position for q 2 in column 3, i.e. We find that if we place q 2 in column 1 and 2, then the dead end is encountered. Next, we put queen q 2 so that both these queens do not attack each other. Now, we place queen q 1 in the very first acceptable position (1, 1). In such a conditional each queen must be placed on a different row, i.e., we put queen 'i' on row 'i.' Since, we have to place 4 queens such as q 1 q 2 q 3 and q 4 on the chessboard, such that no two queens attack each other. Given a 4 x 4 chessboard and number the rows and column of the chessboard 1 through 4. So first we will consider the 4 queens problem and then generate it to n - queens problem. It can be seen that for n =1, the problem has a trivial solution, and no solution exists for n =2 and n =3. N - Queens problem is to place n - queens in such a manner on an n x n chessboard that no queens attack each other by being in the same row, column or diagonal.

Dead space brute location