# codejam 2014 bits xoring

Hey guys am not able to get the idea how to solve the first question
of Codejam Round 1A,Pleae help me out…Thanx in advance

Lets call the two sets of strings we have as given,reqd. Now if it is possible to get reqd from given then reqd[0] must be formed from either given[0] or given[1] … given[n-1].

Check for every value in given which all switches you need to flip to get reqd[0]. Now flip those switches for every value in given. If you get all the elements in reqd by flipping these switches then ans=min(ans,switches flipped).

To see which all switches are flipped you can take an XOR. A 1 will indicate a flipped switch and a 0 will indicate a non-flipped switch.

``````ans=1000000;
for(i=0;i<n;i++)
{
string flip=XOR(given[i],reqd[0]);
string temp[n];
for(j=0;j<n;j++)
{
temp[j]=XOR(given[j],flip);
}
if(all elements of reqd are in temp)
ans=min(ans,number of 1's in flip)
}
``````

Now if ans is still 1000000 that means we haven’t found an answer so print not possible else print ans.

4 Likes

@akulsareen Thanx Yeah now got the concept