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1907. Categorize Salary Counts Table: Accounts +-------------+------+ | Column | Type | +-------------+------+ | account_id | int | | income | int | +-------------+------+ account_id is the primary key. Each row has monthly income of a bank account. Query the number of accounts in each salary category: Low Salary: income < 200 ...

Problem Description Given a non-strictly increasing (sorted with possible duplicates) integer aray nums, remove the duplicates in-place succh that each unique element appears only once. Maintain the relative order of the unique elements and return the number of unique elements in nums. Let k be the count of unique elements. To pass the test cas ...

Problem Understanding The challenge requires removing specific values from an array while meeting these constraints: Use only O(1) additional space and modify the input array in-place Element ordering can be changed Focus only on elements within the new length boundary The solution will be validated using code similar to: int result_length = ...

The three-sum problem requires finding all unique triplets in an array that add up to zero. While depth-first search can solve this after sorting, a more efficient approach uses the two-pointer technique on a sorted array. Key Points Use two pointers, not a single pointer—common mistake to avoid Recommended solving time: 20 minutes Problem De ...

Counting Palindromic Substrings This section addresses the problem of counting all palindromic substrings within a given string, similar to LeetCode problem 647. Problem Description Given a string s, determine and return the total count of palindromic substrings. A substring is a contiguous sequence of charcaters. A palindromic string reads the ...

LeetCode 257: Binary Tree All Paths Termination Condition Considerations The statement if (root == nullptr) return; serves multiple critical purposes in recursive tree algorithms: Primary Function Guard When placed in the main function provided by LeetCode, this check handles the empty tree case. If an empty tree is passed to the main function, ...

590. N-ary Tree Postorder Traversal Approach: Right-to-left, then root-to-left. Use a stack with a visited set to track processed nodes. class Node: def __init__(self, val=None, children=None): self.val = val self.children = children def postorder(root): if not root: return [] stack = [root] result = [] ...

The Trapping Rain Water problem, as featured on LeetCode 42, asks you to calculate the total amount of water that can be trapped after raining, given an elevation map represented by an array of non-negative integers. Each element in the array represents the height of a bar with a width of 1. Water can be trapped between bars of higher elevation ...

Two Sum Use a hash map to store each number’s index. For every element, check if the complement (target - current) exists in the map. class Solution: def twoSum(self, nums: List[int], target: int) -> List[int]: seen = {} for idx, val in enumerate(nums): complement = target - val if complement in se ...

Swapping Adjacent Nodes in a Linked ListSwapping nodes in pairs requires careful pointer manipulation to maintain the integrity of the list structure. The core idea involves processing two nodes at a time, reversing their connection order while preserving links to neighboring nodes.A dummy header node simplifies edge cases by providing a consis ...