Data Structures and Algorithms

recursive helper methods, recursive binary search, recursion vs iteration, exponential recursion, memoization, backtracking (subsets, permutations, N-Queens), StackOverflowError

generic classes, interfaces and methods, diamond <>, bounded types <T extends Comparable<T>>, wildcards ? extends / ? super (PECS), raw types, type erasure

functional interfaces, lambdas, method references, Comparable vs Comparator, Comparator.comparing, streams, collectors, Optional

Collection hierarchy, ArrayList vs LinkedList, Iterator/ListIterator, fail-fast iterators, ArrayDeque as stack and queue, PriorityQueue, Arrays.asList, Collections utilities

HashSet, LinkedHashSet, TreeSet, equals/hashCode, Comparator, NavigableMap, HashMap, TreeMap, merge, computeIfAbsent

RAM model, Big-O / Big-Ω / Big-Θ, growth rates, loop analysis, best/worst/average case, space complexity, amortized analysis, loop invariants

recurrences, iteration and substitution, recursion trees, Master theorem, divide-and-conquer, recursive binary search, merge step, counting inversions, maximum subarray, fast exponentiation

greedy choice property, interval scheduling, fractional knapsack, Huffman coding, optimal substructure, memoization vs tabulation, coin change, 0/1 knapsack, LCS, LIS, solution reconstruction

insertion sort, mergeSort, quick sort (Lomuto), heap sort, counting/radix/bucket sort, stability, Ω(n log n) lower bound, Arrays.sort

List ADT, MyArrayList and ensureCapacity, amortized O(1) append, singly and doubly linked lists, Iterator inner classes, array and linked stacks, circular-array and linked queues

complete binary trees in an array, max-heap and min-heap, sift-up and sift-down, bottom-up buildHeap, heap sort, MyPriorityQueue<E> with a Comparator, top-k and k-way merge, java.util.PriorityQueue

tree vocabulary, the BST property, search and insert, delete (three cases), pre-/in-/post-/level-order traversal, height and O(h) costs, recursive tree utilities, isBST, a BST iterator

height and balance factor, the AVL invariant, LL/RR/LR/RL rotations, rebalancing after insertion and deletion, O(log n) height, red-black trees and TreeMap

hash functions and compression, String.hashCode, separate chaining, linear/quadratic probing, double hashing, load factor, rehashing, tombstones, MyHashMap, equals/hashCode, HashMap internals

graph vocabulary, edge list, adjacency matrix, adjacency lists, BFS, DFS, connected components, cycle detection, bipartite graphs, topological sort, O(V + E)

weighted edges, relaxation, Dijkstra's algorithm, predecessor array, negative weights, Bellman–Ford, minimum spanning trees, cut property, Prim's algorithm, Kruskal's algorithm, union–find