OP1 week ago
Most DSA courses promise to cover “everything,” but for fresher/SDE-1 interviews, you don't need equal depth everywhere.
Arrays and strings are non-negotiable. Master two pointers, sliding window, subarrays, duplicates, and common string patterns. This should be your foundation. Hash maps are extremely important. Many O(n²) brute-force problems become O(n) by using a hash map. Learn to recognize when extra memory can eliminate a loop.
Linked lists appear less often, but know the classics: reverse a list, detect a cycle, and find the middle node. Trees deserve serious attention. Master binary-tree traversals, BST basics, level-order traversal, and recursion. Stacks and queues are smaller but useful for parentheses, next-greater-element, undo operations, and BFS. Unless targeting competitive-programming-heavy companies, deprioritize advanced graphs, segment trees, and difficult DP.
A good split: 60% arrays/strings/hashmaps, 25% trees/recursion, 15% everything else.
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