Combination Sum
Combination Sum (Python)
Stack in Java
Stack using LL Stack using ArrayList Push At Bottom (Question)
Recursion – Permutations
Permutation of String Permutation of Array
Recursion subset or subsequence
Return ArrayList
Sudoku Solver
Suduko Solver (Java) Suduko Solver (Python)
N-Queens Solved
N-Queens (LeetCode)
Maze Problems
We observe that left = r-1, c and right = c, r-1. For counting the total ways just return left + right. Including all paths (Using Backtracking) Output
How Many Numbers Are Smaller Than the Current Number
1365. How Many Numbers Are Smaller Than the Current Number (Easy) Given the array nums, for each nums[i] find out how many numbers in the array are smaller than it. That is, for each nums[i] you have to count the number of valid j’s such that j != i and nums[j] < nums[i]. Return the answer in an array. Example 1: Input: nums = [8,1,2,2,3] Output: … Read more
Number of Good Pairs (LeetCode)
1512. Number of Good Pairs (Easy) Given an array of integers nums, return the number of good pairs. A pair (i, j) is called good if nums[i] == nums[j] and i < j. Example 1: Input: nums = [1,2,3,1,1,3] Output: 4 Explanation: There are 4 good pairs (0,3), (0,4), (3,4), (2,5) 0-indexed. Example 2: Input: nums = [1,1,1,1] Output: 6 Explanation: Each pair in the array are good. … Read more
