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- bobbym
- 2012-11-13 11:11:45
Hi Blitz;
You are welcome. You understood that fast, very good.
- Blitz
- 2012-11-13 11:05:54
I get it now. Thanks for explaining!
- bobbym
- 2012-11-12 11:26:33
Hi;
Supposing we have {4,7,9,10,11} out of the numbers 1 to 20.
The first combination is 1,2,3,4,5 and the last is 16,17,18,19,20.
Start with the first number which is 4.
There are 19 C 4 combinations of the type 1,xxxx
There are 18 C 4 combinations of the type 2,xxxx
There are 17 C 4 combinations of the type 3,xxxx
so we have
There are 15 C 3 combinations of the type 4,5 xxx
There are 14 C 3 combinations of the type 4,6 xxx
so we have
There are 12 C 2 combinations of the type 4,7,8 xx
so we have
add 1 for the next one.
Want to do another?
- Blitz
- 2012-11-12 11:01:04
Blitz wrote:
So here's the same question : Can you explain your example please, because I don't see how {4,7,9,10,11} results in your algorithm. I don't see the link between 4,7,9,10,11 and the numbers in your algorithm:
Thx for clarifying the second question.
- bobbym
- 2012-11-10 11:47:27
Hi Blitz;
Like with the permutations there is no formula just an algorithm or method.
For the second question:
so
- Blitz
- 2012-11-10 09:32:43
bobbym wrote:
A couple of questions, usually formulas are given for permutations.
Do you want {1,2,3,4,5} to be different than {5,4,3,2,1}?]
No, so I think we're talking about combinations here.
Can you explain your example please, because I don't see how {4,7,9,10,11} results in your formula
and how do you write
- bobbym
- 2012-11-08 10:56:34
Hi Blitz;
A couple of questions, usually formulas are given for permutations.
Do you want {1,2,3,4,5} to be different than {5,4,3,2,1}? Then we are dealing with a permutation.
There is an algorithm to do this:
Let's say you want the position and I have picked small numbers to better illustrate, {4,7,9,10,11}
For {1,2,3,4,7} we get:
- Blitz
- 2012-11-08 10:25:20
Hi,
I`ve carefully read this site's in depth explanation regarding combinations and permutations and I`ve learned a lot.
However... I have two questions:
1. I am still searching a formula that can give me the RANKING POSITION of a combination. I`ll give an example:
lottery numbers : 5 numbers are chosen from 50 numbers. this gives 2118760 possible combinations, from 1-2-3-4-5 to 46-47-48-49-50.
Now I need a formula that gives me the ranking position (from 1 to 2118760), when I enter the 5 chosen numbers in the formula. For example, combination 1-2-3-4-6 should return ranking position #2, combination 1-2-3-4-7 should return 3, and so on.
What is the formula for this?
2. I have noticed that the Combinations and Permutations Calculator on this site calculates the result at any keystroke. This makes me believe it uses a non-recursive factorial function. So far, I haven't found any non-recursive factorial math function (to use in visual basic for example). I have used a recursive factorial function so far, but when the number of possible combinations gets too high, I get -an expected- stack overflow. What function does this website use?