Thread: find the k-th smallest element in O(logk) time

Please give me a hand to deal with it!

3 array A[1:l], B[1:m],C[1:n], all sorted in

increasing order. for a integer 1<=k<=l+m+n, find an

algorithm to find the k-th smallest element in the

merge of A,B,C in O(logk) time. (assume that there's

no duplicate numbers in A,B,C)

hint : look at the quick sort algorithm carefully .
HW ????

I dont understand .
the quick sort algorithm sort n elements in O(nlogn) time.