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Coding

Big-O Complexity Flashcards

34 cards · EN → EN · Coding

Master algorithm time and space complexity analysis. Covers all major complexity classes, common algorithm complexities, data structure operation costs, and key rules for calculating Big-O. Essential for coding interviews and writing efficient software.

This page covers Big-O Complexity: 34 flashcards in the coding category. Cards are oriented around the EN → EN language pair, so each prompt trains recognition in the direction you actually need. Difficulty is tagged intermediate, so you can expect a intermediate-friendly progression rather than a random dump of trivia.

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First 20 cards from this deck (front / back).

#FrontBack
1What is Big-O notation?A mathematical notation describing the upper bound (worst-case) growth rate of an algorithm's time or space requirements as input size n grows toward infinity. It ignores constants and low-order terms.
2O(1) — Constant TimeExecution time does NOT grow with input size. Single operation regardless of n. The best possible complexity.
3O(log n) — Logarithmic TimeTime grows proportional to log₂(n). Each step halves (or divides) the problem. Doubling input adds only ONE more step. Excellent for large datasets.
4O(n) — Linear TimeTime grows directly proportional to input size. If n doubles, time doubles. Typically means visiting each element once.
5O(n log n) — Linearithmic TimeSlightly worse than linear. Common in divide-and-conquer sorting algorithms. Often considered the theoretical minimum for comparison-based sorting.
6O(n²) — Quadratic TimeTime grows as the square of input size. Doubling n quadruples the time. Usually appears with nested loops over the same data.
7O(n³) — Cubic TimeTime grows as the cube of input size. Typically three nested loops. Practical only for very small inputs.
8O(2ⁿ) — Exponential TimeTime doubles with each additional input element. Quickly becomes infeasible even for moderate n. Often arises in brute-force recursive algorithms.
9O(n!) — Factorial TimeTime grows factorially with input size. Even n=20 produces 2.4 quintillion operations. Only feasible for tiny inputs (n < ~12).
10Big-O Complexity Order (best to worst)O(1) < O(log n) < O(√n) < O(n) < O(n log n) < O(n²) < O(n³) < O(2ⁿ) < O(n!)
11Rule: Drop ConstantsBig-O ignores constant multipliers. O(2n), O(100n), and O(0.001n) are all O(n). Constants don't affect the growth class.
12Rule: Drop Non-Dominant TermsKeep only the fastest-growing term. O(n² + n) = O(n²). O(2ⁿ + n³) = O(2ⁿ).
13Rule: Different Variables for Different InputsIf an algorithm processes two independent inputs of sizes n and m, the complexity is O(n + m) or O(n × m), NOT O(n²).
14Space ComplexityAmount of extra memory an algorithm uses relative to input size n. Measured the same way as time complexity. Input itself doesn't count (only auxiliary space).
15Array — AccessO(1) — Direct index access
16Array — Search (unsorted)O(n) — Must check every element in worst case
17Array — Insert/Delete (end)O(1) amortized for dynamic arrays (e.g., push/pop at end)
18Array — Insert/Delete (middle)O(n) — Must shift elements to fill the gap or make room
19Hash Map — Lookup / Insert / DeleteO(1) average case. O(n) worst case (all keys collide — extremely rare with good hash functions).
20Binary Search Tree (balanced) — Search/Insert/DeleteO(log n) for balanced BST (AVL, Red-Black). O(n) worst case for degenerate (unbalanced) BST.

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