Generalized Permutations and Combinations
Generating Permutations and Combinations
Permutations & Combinations
Patrick McAtee, Tom Rice, and Jesse Whidden
Generalized Permuations and Combinations
Repetitions, Indistinguishable Objects, and Objects in Boxes
Repetitions Summary
In this section, we've examined how repetition or sampling with replacement can change the number of possibilities, or the probability of an event. Whenever you're calculating combinations, it's important to first identify the n and r values.
Remember that n is always the number of things you have to choose from and r is always how many of those items you want to pick.
Here is a summary of the main formulas introduced so far:
| Summary | Repetition Allowed | Repetition not Allowed |
| r-permutations | nr | n! (n-r)! |
| r-combinations | (n+r-1)! r!(n-1)! |
n! r!(n-r)! |
For comparison, here is an example of how the different formulas can afffect your final answer:
Source code: pcApp.java
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| Previous: Combinations with Repetition | Next: Indistinguishable Objects and Objects in Boxes |
Last updated 12/14/2001