it's exactly the same question as Buttons on codechef. search this forum , it have been discussed before
On Tue, Jan 4, 2011 at 4:13 PM, bittu <[email protected]> wrote: > There is a lock which is an N by N grid of switches. Each switch can > be in one of two states (on/off). The lock is unlocked if all the > switches are on. The lock is built in such a way that, if you toggle > some switch, all the switches in its row and its column toggle too > > Give an algorithm which, given N and a configuration of the N^2 > switches, will tell you whether the lock can be unlocked by a sequence > of switch toggles > > Note 1: Can be done in O(N^2) time and O(1) space. > Note 2: You just need to tell if a sequence which unlocks the lock > exists (and not the actual sequence) > > -- > You received this message because you are subscribed to the Google Groups > "Algorithm Geeks" group. > To post to this group, send email to [email protected]. > To unsubscribe from this group, send email to > [email protected]<algogeeks%[email protected]> > . > For more options, visit this group at > http://groups.google.com/group/algogeeks?hl=en. > > -- You received this message because you are subscribed to the Google Groups "Algorithm Geeks" group. To post to this group, send email to [email protected]. To unsubscribe from this group, send email to [email protected]. For more options, visit this group at http://groups.google.com/group/algogeeks?hl=en.
