Combinatorics Questions

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Combinations nCr Small

Medium
2 views 25 Jan 2026
Compute nCr for small n (n...
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Permutations nPr

Easy
2 views 25 Jan 2026
Compute nPr = n*(n-1)*...*(n-r+1)....
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Count Binary Strings Without Consecutive 1s

Hard
4 views 25 Jan 2026
Given n, count length-n binary strings with no '11'....
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Handshake Problem

Easy
3 views 25 Jan 2026
If there are n people and everyone shakes hands once, how many handshakes?...
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Choose Team With Captain

Medium
4 views 25 Jan 2026
Choose r people from n and also pick a captain from chosen team....
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Stars And Bars

Hard
3 views 25 Jan 2026
Count solutions of x1+...+xk = n with xi>=0....
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Count Subsets Size K

Easy
2 views 25 Jan 2026
Given n and k, count k-sized subsets....
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Binomial Identity Check

Medium
4 views 25 Jan 2026
Compute sum_{i=0..k} C(n,i) for given n,k....
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Circular Arrangements

Easy
2 views 25 Jan 2026
Count ways to arrange n distinct items on a circle....
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Derangements Small

Hard
4 views 25 Jan 2026
Compute number of derangements for n...
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