1. "RE: Permutation Expression"
In response to message #0
Think of it the following way. Elements 0, 1, ..., k-1 are fixed. Draw the number line and vertical bars at k points which should be denoted 0, 1, ..., k-1. This bars divide the line into k+1 buckets. The question is now, in how many ways can you put the remaining n-k elements into those k+1 buckets? This is the same as askng, in how many ways n-k buckets can be selected out of k+1 with repitions allowed?
Printer-friendly copy
Email this topic to a friend
