25 Questions

Graphs:

1. Clone Graph:Graph

   https://lnkd.in/dV2P2TEs

2. Course Schedule: https://lnkd.in/de8Q3NBS

3. 01 Matrix:Matrix

   https:

   Given an m x n binary matrix mat, return the distance of the nearest 0 for each cell.

   The distance between two cells sharing a common edge is 1.

   Example 1:

   

   Input: mat = [[0,0,0],[0,1,0],[0,0,0]] Output: [[0,0,0],[0,1,0],[0,0,0]]

   class Solution {
       public int[][] updateMatrix(int[][] mat) {
           int m = mat.length;           //lnkd.in/dV2P2TEs

 Number of rows int n = mat[0].length; // Number of columns Queue<int[]> queue = new LinkedList<>(); // Queue to perform BFS // Initialize matrix: // Add all 0s to the queue and mark all 1s as unvisited (-1) for(int i = 0; i < m; i++){ for(int j = 0; j < n; j++){ if(mat[i][j] == 0){ // Add coordinates of 0s to the queue as starting points queue.add(new int[]{i, j}); } else { // Mark 1s as -1 to indicate they haven't been processed yet mat[i][j] = -1; } } } // Directions to move in the matrix: up, down, left, right int[][] directions = new int[][]{ {-1, 0}, // Up {1, 0}, // Down {0, -1}, // Left {0, 1} // Right }; // Perform BFS from all 0s simultaneously while(!queue.isEmpty()){ int[] curr = queue.poll(); // Current cell coordinates int currRow = curr[0]; int currCol = curr[1]; // Explore all four directions for(int[] direction : directions){ int row = currRow + direction[0]; int col = currCol + direction[1]; // Check bounds and whether the cell is unvisited if(row < 0 || row >= m || col < 0 || col >= n || mat[row][col] != -1){ continue; // Skip invalid or already visited cells } // Update the distance and enqueue the cell mat[row][col] = mat[currRow][currCol] + 1; queue.add(new int[]{row, col}); } } // Return the updated matrix with minimum distances to 0 return mat; } }
5. Number of Islands: https://lnkd.in/drT2MpTz
6. Rotting Oranges: https://lnkd.in/dUQVwJ-d

Arrays:

6. Insert Interval: https://lnkd.in/dfcEDFwB
7. 3Sum: https://lnkd.in/duGvuCjf
8. Product of Array Except Self: https://lnkd.in/dkGkjQVk
9. Combination Sum: https://lnkd.in/d3iStbGc
10. Merge Intervals: https://lnkd.in/dmFZxrVQ

Stacks:

11. Evaluate Reverse Polish Notation: https://lnkd.in/d-y7Zw4C
12. Min Stack: https://lnkd.in/dqbh7PeV
13. Trapping Rain Water: https://lnkd.in/dS_svBAm

Binary Trees:

14. Binary Tree Level Order Traversal: https://lnkd.in/dM-VYbVB
15. Lowest Common Ancestor of a Binary Tree: https://lnkd.in/dUvJykgA
16. Serialize and Deserialize Binary Tree: https://lnkd.in/dW2cP5Wn

Dynamic Programming:

17. Maximum Subarray: https://lnkd.in/dvjYye6E
18. Coin Change: https://lnkd.in/d7zZRg7H

Binary Search:

19. Search in Rotated Sorted Array: https://lnkd.in/dEuh3gie
20. Time-Based Key-Value Store: https://lnkd.in/dbERGKUB

Strings:

21. Longest Substring Without Repeating Characters: https://lnkd.in/d_vZrZda
22. Minimum Window Substring: https://lnkd.in/de8aeeQD

Heap:

23. K Closest Points to Origin: https://lnkd.in/dUtCqYf4
24. Find Median from Data Stream: https://lnkd.in/ddDgWqUv

Recursion:

25. Permutations: https://lnkd.in/dTUqmAfy