Focused topic

Combinations and Permutations quant interview practice.

Combinations and permutations problems reward precise modeling more than memorized formulas. The reviewed questions cover ordered arrangements, subsets, repeated objects, circular structures, card selections, digit restrictions, and probability calculations built on counting. Before writing a binomial coefficient, identify the objects, available positions, replacement rule, and whether two outcomes that differ only by order should be distinct. A useful second check is to solve by complementary counting or by multiplying sequential choices and confirm that both approaches agree. Several exercises deliberately combine multiple cases, making disjointness and avoidance of double counting essential. Candidates should narrate why each factor or combination appears, rather than presenting a compact expression without interpretation. This collection is kept separate from the broader Combinatorics tag to target the specific search intent around arrangements and selections.

Reviewed questions

39

Library records

315

Easy

27

Hard