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ProblemGiven an integer array nums, return the length of the longest strictly increasing subsequence . Example 1: 1234Input: nums = [10,9,2,5,3,7,101,18]Output: 4Explanation: The longest increasing subsequence is [2,3,7,101], therefore the length is 4. Example 2: 123Input: nums = [0,1,0,3,2,3]Output: 4 Example 3: 123Input: nums = [7,7,7,7,7,7,7]Output: 1 Constraints: 1 <= nums.length <= 2500 104 <= nums[i] <= 104 Follow up: Can you come up with an algorithm that runs in O(n log( ...

ProblemGiven an array arr of 4 digits, find the latest 24-hour time that can be made using each digit exactly once. 24-hour times are formatted as "HH:MM", where HH is between 00 and 23, and MM is between 00 and 59. The earliest 24-hour time is 00:00, and the latest is 23:59. Return the latest 24-hour time in "HH:MM" format. If no valid time can be made, return an empty string. Example 1: 1234Input: arr = [1,2,3,4]Output: "23:41"Explanation: The valid 24-hour times ...

ProblemThere are n gas stations along a circular route, where the amount of gas at the ith station is gas[i]. You have a car with an unlimited gas tank and it costs cost[i] of gas to travel from the ith station to its next (i + 1)th station. You begin the journey with an empty tank at one of the gas stations. Given two integer arrays gas and cost, return the starting gas station’s index if you can travel around the circuit once in the clockwise direction, otherwise return -1. If there exists a s ...

ProblemGiven a reference of a node in a connected undirected graph. Return a deep copy (clone) of the graph. Each node in the graph contains a value (int) and a list (List[Node]) of its neighbors. 12345class Node { public int val; public List<Node> neighbors;} Test case format: For simplicity, each node’s value is the same as the node’s index (1-indexed). For example, the first node with val == 1, the second node with val == 2, and so on. The graph is represented in the te ...

ProblemGiven two strings s and t, determine if they are isomorphic. Two strings s and t are isomorphic if the characters in s can be replaced to get t. All occurrences of a character must be replaced with another character while preserving the order of characters. No two characters may map to the same character, but a character may map to itself. Example 1: Input: s = “egg”, t = “add” Output: true Explanation: The strings s and t can be made identical by: Mapping 'e' to 'a ...

ProblemGiven two strings ransomNote and magazine, return true if ransomNote can be constructed by using the letters from magazine and false otherwise. Each letter in magazine can only be used once in ransomNote. Example 1: 123Input: ransomNote = "a", magazine = "b"Output: false Example 2: 12Input: ransomNote = "aa", magazine = "ab"Output: false Example 3: 123Input: ransomNote = "aa", magazine = "aab"Output: true Constraints: 1 <= ...

ProblemGiven a string s containing just the characters '(', ')', '{', '}', '[' and ']', determine if the input string is valid. An input string is valid if: Open brackets must be closed by the same type of brackets. Open brackets must be closed in the correct order. Every close bracket has a corresponding open bracket of the same type. Example 1: 123Input: s = "()"Output: true Example 2: 123Input: s = "()[]{}&q ...

ProblemThere are n computers numbered from 0 to n - 1 connected by ethernet cables connections forming a network where connections[i] = [ai, bi] represents a connection between computers ai and bi. Any computer can reach any other computer directly or indirectly through the network. You are given an initial computer network connections. You can extract certain cables between two directly connected computers, and place them between any pair of disconnected computers to make them directly connecte ...

ProblemGiven the root of a binary tree, flatten the tree into a “linked list”: The “linked list” should use the same TreeNode class where the right child pointer points to the next node in the list and the left child pointer is always null. The “linked list” should be in the same order as a pre-order traversal of the binary tree. Example 1: !https://assets.leetcode.com/uploads/2021/01/14/flaten.jpg 123Input: root = [1,2,5,3,4,null,6]Output: [1,null,2,null,3,null,4,null,5,null,6] Example 2: 1 ...

ProblemGiven a root node reference of a BST and a key, delete the node with the given key in the BST. Return the root node reference (possibly updated) of the BST. Basically, the deletion can be divided into two stages: Search for a node to remove. If the node is found, delete the node. Example 1: !https://assets.leetcode.com/uploads/2020/09/04/del_node_1.jpg 123456Input: root = [5,3,6,2,4,null,7], key = 3Output: [5,4,6,2,null,null,7]Explanation: Given key to delete is 3. So we find the node ...