I meant to ask, what parttens of algorithm and datastructure should I be considering if I need to solve hackerrank problems?

1. **Sorting Algorithms**:

- Bubble Sort

- Insertion Sort

- Selection Sort

- Merge Sort (Divide and Conquer)

- QuickSort (Divide and Conquer)

2. **Searching Algorithms**:

- Linear Search

- Binary Search

3. **Graph Traversal Techniques**:

- Depth-First Search (DFS)

`java

void dfs(int node, boolean[] visited) {

if (!visited[node]) {

// Process the current node

for (int neighbor : adjList.get(node)) {

dfs(neighbor, visited);

}

}

}

`

- Breadth-First Search (BFS)

`java

void bfs(int start) {

Queue queue = new LinkedList<>();

boolean[] visited = new boolean[numVertices];

visited[start] = true;

queue.add(start);

while (!queue.isEmpty()) {

int current = queue.poll();

// Process the current node

for (int neighbor : adjList.get(current)) {

if (!visited[neighbor]) {

visited[neighbor] = true;

queue.add(neighbor);

}

}

}

}

4. **Dynamic Programming**:

- Memoization

- Tabulation

5. **Greedy Algorithms**:

- Fractional Knapsack Problem

- Minimum Spanning Tree (Kruskal's and Prim's)

`java

class Edge implements Comparable {

int src, dest, weight;

public int compareTo(Edge other) {

return this.weight - other.weight;

}

}

void kruskalMST(int V, Edge[] edges) {

Arrays.sort(edges);

int parent[] = new int[V];

makeSet(parent);

}

void union(int x, int y, Edge e) {

// Implement the logic to unite sets

}

6. **Divide and Conquer**:

- Binary Search (as mentioned earlier)

- Merge Sort

7. **Backtracking**:

- N-Queens Problem

`java

boolean solveNQUtil(int board[][], int col) {

if (col >= n)

return true;

for (int i = 0; i < N; i++) {

// If it is safe to place this queen in board[i][col], then

if (isSafe(board, i, col)) {

/* Place the Queen */

board[i][col] = 1;

// recur to place rest of queens

if (solveNQUtil(board, col + 1))

return true;

}

/* If placing queen in board[i][col] doesn't lead to a solution

then remove queen from board[i][col] */

board[i][j]=0;

}

/* If the Queen can not be placed in any row in this column col then return false */

}

`

8. **Sliding Window**:

- Maximum Subarray Sum

`java

int maxSubArraySum(int a[],int size) {

int max_so_far = Integer.MIN_VALUE,

curr_max = 0;

for (int i=0; i < size; i++)

{

curr_max += a[i];

if(max_so_far < curr_max)

max_so_far = curr_max;

/* If current sum becomes negative, then change it to 0*/

if(curr_max < 0)

curr_max=0;

}

return max_so_far;

}

9. **Two Pointers**:

- Two Sum Problem

`java

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

HashMap map = new HashMap<>();

for (int i=0; i

if(map.containsKey(target- nums[i]))

return new int[] { map.get(target - nums[i]),i };

else

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

throw new IllegalArgumentException("No two sum solution");

}

`

10. **Bit Manipulation**:

- Binary Representation and Operations

By mastering these patterns, you'll be well-equipped to tackle a wide range of HackerRank problems efficiently.