recursion figure representing an board using - array figure in which three queens have been placed and we need to determine if the square at position ( is unguarded when searching horizontally backwardwe examine the elements of the - array looking for an index equal to that of the current row if one is foundthen there is queen already positioned on the current row as is the case in this example if queen was not found on the current rowthen we would have to search diagonally to the upper left and to the lower left in these two caseswe search the squares indicated by the arrows and examine the row indices of each and compare them to the entries in the - array if any of the indices matchthen queen is currently guarding the position and it is not legal move figure determining if square is unguarded using - array