Q1. O(NlogN)

Q2. O((logN)*(logN)) which is also written as O(log2N). Note that
log2N is different from logN2. The former is (logN)*(logN), where as 
the latter is log(N*N), which is same as 2*logN

Q3. O(min(n,m)). Download this piece of  Code  and see the result 
printed out for various values of n and m. 

Q4. O(N2logN)