Given a pattern and a string s, return true if s matches the pattern. A string s matches a pattern if there is some bijective mapping of single characters to strings such that if each character in pattern is replaced by the string it maps to, then the resulting string is s. A bijective mapping means that no two characters map to the same string, and no character maps to two different strings. ...
You are given an array routes representing bus routes where routes[i] is a bus route that the ith bus repeats forever. For example, if routes[0] = [1, 5, 7], this means that the 0th bus travels in the sequence 1 -> 5 -> 7 -> 1 -> 5 -> 7 -> 1 -> … forever. You will start at the bus stop source (You are not on any bus initially), and you want to go to the bus stop target. You can travel between bus stops by buses only. ...
We can shift a string by shifting each of its letters to its successive letter. For example, “abc” can be shifted to be “bcd”. We can keep shifting the string to form a sequence. For example, we can keep shifting “abc” to form the sequence: “abc” -> “bcd” -> … -> “xyz”. Given an array of strings strings, group all strings[i] that belong to the same shifting sequence. You may return the answer in any order. ...
Given two strings s and t of lengths m and n respectively, return the minimum window substring of s such that every character in t (including duplicates) is included in the window. If there is no such substring, return the empty string “”. The testcases will be generated such that the answer is unique. A substring is a contiguous sequence of characters within the string. Example 1: Input: s = "ADOBECODEBANC", t = "ABC" Output: "BANC" Explanation: The minimum window substring "BANC" includes 'A', 'B', and 'C' from string t. Example 2: Input: s = "a", t = "a" Output: "a" Explanation: The entire string s is the minimum window. Example 3: Input: s = "a", t = "aa" Output: "" Explanation: Both 'a's from t must be included in the window. Since the largest window of s only has one 'a', return empty string. Constraints: ...
A parentheses string is valid if and only if: It is the empty string, It can be written as AB (A concatenated with B), where A and B are valid strings, or It can be written as (A), where A is a valid string. You are given a parentheses string s. In one move, you can insert a parenthesis at any position of the string. ...
Given the root of a binary tree, return all root-to-leaf paths in any order. A leaf is a node with no children. Example 1: Input: root = [1,2,3,null,5] Output: ["1->2->5","1->3"] Example 2: Input: root = [1] Output: ["1"] Constraints: The number of nodes in the tree is in the range [1, 100]. -100 <= Node.val <= 100 Solution /** * Definition for a binary tree node. * public class TreeNode { * int val; * TreeNode left; * TreeNode right; * TreeNode() {} * TreeNode(int val) { this.val = val; } * TreeNode(int val, TreeNode left, TreeNode right) { * this.val = val; * this.left = left; * this.right = right; * } * } */ class Solution { public List<String> binaryTreePaths(TreeNode root) { List<String> res = new ArrayList<>(); dfs(root, res, ""); return res; } void dfs(TreeNode node, List<String> res, String s) { if (node == null) { return; } if (s.length() == 0) { s += "" + node.val; } else { s += "->" + node.val; } if (node.left == null && node.right == null) { res.add(s); return; } dfs(node.left, res, s); dfs(node.right, res, s); } }
Given a collection of numbers, nums, that might contain duplicates, return all possible unique permutations in any order. Example 1: Input: nums = [1,1,2] Output: [[1,1,2], [1,2,1], [2,1,1]] Example 2: Input: nums = [1,2,3] Output: [[1,2,3],[1,3,2],[2,1,3],[2,3,1],[3,1,2],[3,2,1]] Constraints: 1 <= nums.length <= 8 -10 <= nums[i] <= 10 Solution class Solution { public List<List<Integer>> permuteUnique(int[] nums) { List<List<Integer>> res = new ArrayList<>(); permuteAt(0, nums, res); return res; } void permuteAt(int i, int[] nums, List<List<Integer>> res) { if (i == nums.length) { res.add(toList(nums)); return; } Set<Integer> seen = new HashSet<>(); for (int j = i; j < nums.length; j++) { if (seen.add(nums[j])) { swap(i, j, nums); permuteAt(i + 1, nums, res); swap(i, j, nums); } } } void swap(int i, int j, int[] arr) { int t = arr[i]; arr[i] = arr[j]; arr[j] = t; } List<Integer> toList(int[] values) { List<Integer> res = new ArrayList<>(values.length); for (int val : values) { res.add(val); } return res; } }
Given two strings s and t, return true if they are both one edit distance apart, otherwise return false. A string s is said to be one distance apart from a string t if you can: Insert exactly one character into s to get t. Delete exactly one character from s to get t. Replace exactly one character of s with a different character to get t. Example 1: Input: s = "ab", t = "acb" Output: true Explanation: We can insert 'c' into s to get t. Example 2: Input: s = "", t = "" Output: false Explanation: We cannot get t from s by only one step. Example 3: Input: s = "a", t = "" Output: true Example 4: Input: s = "", t = "A" Output: true Constraints: ...
Given a string queryIP, return “IPv4” if IP is a valid IPv4 address, “IPv6” if IP is a valid IPv6 address or “Neither” if IP is not a correct IP of any type. A valid IPv4 address is an IP in the form “x1.x2.x3.x4” where 0 <= xi <= 255 and xi cannot contain leading zeros. For example, “192.168.1.1” and “192.168.1.0” are valid IPv4 addresses but “192.168.01.1”, while “192.168.1.00” and “192.168@1.1” are invalid IPv4 addresses. ...
You are given two lists of closed intervals, firstList and secondList, where firstList[i] = [starti, endi] and secondList[j] = [startj, endj]. Each list of intervals is pairwise disjoint and in sorted order. Return the intersection of these two interval lists. A closed interval [a, b] (with a <= b) denotes the set of real numbers x with a <= x <= b. The intersection of two closed intervals is a set of real numbers that are either empty or represented as a closed interval. For example, the intersection of [1, 3] and [2, 4] is [2, 3]. ...