1. Problem Summary You are given an integer n, and you must count how many permutations of numbers 1 through n satisfy the following condition: For every position i (1-based index): These permutations are called Beautiful Arrangements. Your task is to return the total number of such valid permutations. Example interpretation:If n = 2, the…

1. Problem Summary You are given: Your task is to: Return the node in the cloned tree that corresponds to the target node in the original tree. Important details: The output must be a reference to the matching node in the cloned tree. 2. Key Insights Value comparison is not reliable Because multiple nodes can…

1. Problem Summary You are given: Your task is to determine whether arr can be formed by concatenating the arrays in pieces in any order, with these rules: Return: Example interpretation:Input: We can concatenate [85] + [1,2] to form [85,1,2] → return true. 2. Key Insights Each subarray in pieces must match starting from some…

1. Problem Summary You are given an integer array nums that: You are also given an integer target. Your task is to determine whether target exists in the array.Return: Example interpretation:If nums = [2,5,6,0,0,1,2] and target = 0, the answer is true.If target = 3, the answer is false. 2. Key Insights This problem differs…

1. Problem Summary You are given an encoded string s that follows a specific pattern, and your task is to decode it. The encoding rules are: Where: Example interpretation:Input: Decoding steps: Final output: 2. Key Insights Nested encodings require a stack-based solution You cannot decode from left to right in a single pass without remembering…

1. Problem Summary You are given an array of intervals, where each interval is represented as: Your task is to: Important details: Example:Input: Output: Because [1,3] and [2,6] overlap and merge into [1,6]. 2. Key Insights 1. Sorting by start time is crucial If intervals are sorted by their start value: 2. When do intervals…

1. Problem Summary You are given four points in a 2D plane.Each point is represented by a pair of integers: Your task is to determine whether these four points form a square, regardless of their ordering. To be considered a valid square: Example interpretation:If the points are: These form a perfect square → return true.…

1. Problem Summary You are given a binary matrix image where each entry is either: Your task is to transform the matrix by performing two operations on each row: Finally, return the resulting matrix. Example interpretation:If a row is: After flipping: After inverting: 2. Key Insights Flip and invert can be combined in one pass…

1. Problem Summary You are given the root of a binary tree.Your task is to compute the total tilt of the tree, where: Important details: Example interpretation:If a node has left subtree sum = 10 and right subtree sum = 4, its tilt is: 2. Key Insights Subtree sums must be computed for every node…

1. Problem Summary You are given: Your task is to find the smallest positive integer divisor such that: Important characteristics: Example interpretation:If nums = [1,2,5,9] and threshold = 6, the smallest divisor that keeps the ceiling-sum ≤ 6 is 5. 2. Key Insights Ceiling division is required Formula: Relationship between divisor and sum Meaning: Monotonic…