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Master DSA &
System Design

Your ultimate compendium for interview prep. Master Data Structures, logic building, and scalable System Design through structured roadmaps.

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Curated problem sheets to keep you on track.

Visual dry-runs from brute-force to optimal solutions.

Built specifically for passing technical interviews.

TwoSum.javaInvertTree.javaLRUCache.java

1public int[] twoSum(int[] nums, int target) {

2Map<Integer, Integer> map = new HashMap<>();

3for (int i = 0; i < nums.length; i++) {

4int comp = target - nums[i];

5if (map.containsKey(comp))

6return new int[] {map.get(comp), i};

7map.put(nums[i], i);

9return new int[] {};

10}

1public TreeNode invertTree(TreeNode root) {

2if (root == null) {

3return null;

5// Swap children

6TreeNode temp = root.left;

7root.left = root.right;

8root.right = temp;

9// Recurse down the tree

10invertTree(root.left);

11invertTree(root.right);

12return root;

13}

1public void put(int key, int value) {

2if (cache.containsKey(key)) {

3Node node = cache.get(key);

4node.value = value;

5remove(node);

6insert(node);

7} else {

8if (cache.size() == capacity) {

9cache.remove(tail.prev.key);

10remove(tail.prev);

11}

12Node newNode = new Node(key, value);

13cache.put(key, newNode);

14insert(newNode);

15}

16}

➜~/codeloft/dsajavac TwoSum.java && java Runner

All 45 test cases passed. [Time: 1ms]

➜~/codeloft/dsajavac InvertTree.java && java Runner

Tree successfully inverted. [Time: 2ms]

➜~/codeloft/dsajavac LRUCache.java && java Runner

Cache operations verified. [Time: 3ms]

Arrays & Hashing

O(N) Time / O(N) Space

Binary Trees

O(N) Time / O(H) Space

Enterprise Design

O(1) Time / O(N) Space

Master DSA & System Design

Master DSA &
System Design