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. 1 2 3 4 5 6 7 8 9 Example 1: Input: root = [1,2,3,null,5] Output: ["1->2->5","1->3"] Example 2: Input: root = [1] Output: ["1"] Constraints: ...
Given a collection of numbers, nums, that might contain duplicates, return all possible unique permutations in any order. 1 2 3 4 5 6 7 8 9 10 11 12 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: ...
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. 1 2 3 4 5 Example 1: Input: s = "ab", t = "acb" Output: true Explanation: We can insert 'c' into s to get t. 1 2 3 4 5 Example 2: Input: s = "", t = "" Output: false Explanation: We cannot get t from s by only one step. 1 2 3 4 Example 3: Input: s = "a", t = "" Output: true 1 2 3 4 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]. ...
A phrase is a palindrome if, after converting all uppercase letters into lowercase letters and removing all non-alphanumeric characters, it reads the same forward and backward. Alphanumeric characters include letters and numbers. Given a string s, return true if it is a palindrome, or false otherwise. 1 2 3 4 5 Example 1: Input: s = "A man, a plan, a canal: Panama" Output: true Explanation: "amanaplanacanalpanama" is a palindrome. 1 2 3 4 5 Example 2: Input: s = "race a car" Output: false Explanation: "raceacar" is not a palindrome. 1 2 3 4 5 6 Example 3: Input: s = " " Output: true Explanation: s is an empty string "" after removing non-alphanumeric characters. Since an empty string reads the same forward and backward, it is a palindrome. Constraints: ...
Given the root of a binary search tree, return a balanced binary search tree with the same node values. If there is more than one answer, return any of them. A binary search tree is balanced if the depth of the two subtrees of every node never differs by more than 1. 1 2 3 4 5 Example 1: Input: root = [1,null,2,null,3,null,4,null,null] Output: [2,1,3,null,null,null,4] Explanation: This is not the only correct answer, [3,1,4,null,2] is also correct. ...
Given a string num that contains only digits and an integer target, return all possibilities to insert the binary operators ‘+’, ‘-’, and/or ‘*’ between the digits of num so that the resultant expression evaluates to the target value. Note that operands in the returned expressions should not contain leading zeros. 1 2 3 4 5 Example 1: Input: num = "123", target = 6 Output: ["1*2*3","1+2+3"] Explanation: Both "1*2*3" and "1+2+3" evaluate to 6. 1 2 3 4 5 Example 2: Input: num = "232", target = 8 Output: ["2*3+2","2+3*2"] Explanation: Both "2*3+2" and "2+3*2" evaluate to 8. 1 2 3 4 5 6 Example 3: Input: num = "105", target = 5 Output: ["1*0+5","10-5"] Explanation: Both "1*0+5" and "10-5" evaluate to 5. Note that "1-05" is not a valid expression because the 5 has a leading zero. 1 2 3 4 5 6 Example 4: Input: num = "00", target = 0 Output: ["0*0","0+0","0-0"] Explanation: "0*0", "0+0", and "0-0" all evaluate to 0. Note that "00" is not a valid expression because the 0 has a leading zero. 1 2 3 4 5 Example 5: Input: num = "3456237490", target = 9191 Output: [] Explanation: There are no expressions that can be created from "3456237490" to evaluate to 9191. Constraints: ...
You are given two integer arrays nums1 and nums2, sorted in non-decreasing order, and two integers m and n, representing the number of elements in nums1 and nums2 respectively. Merge nums1 and nums2 into a single array sorted in non-decreasing order. The final sorted array should not be returned by the function, but instead be stored inside the array nums1. To accommodate this, nums1 has a length of m + n, where the first m elements denote the elements that should be merged, and the last n elements are set to 0 and should be ignored. nums2 has a length of n. ...