sol-2.43.tex

This interchange of nested mappings has the effect of exponentially increasing the number of times the procedure `queen-cols` gets computed.  In fact, in order to compute `(queen-cols k)` with this interchanged version, `(queen-cols (- k 1))` needs to be recursively computed a number of times equal to the `board-size`, instead of only once, as was in the original version of exercise~\ref[2.42].\mnote{Estimate how long it'll take to solve the eight-queens puzzle with this new interchanged version!}