Given an array of intervals where intervals[i] = [starti, endi], merge all overlapping intervals, and return an array of the non-overlapping intervals that cover all the intervals in the input.
Given an array of intervals where intervals[i] = [starti, endi], merge all overlapping intervals, and return an array of the non-overlapping intervals that cover all the intervals in the input.
Given an m x n 2D binary grid grid which represents a map of ‘1’s (land) and ‘0’s (water), return the number of islands.
An island is surrounded by water and is formed by connecting adjacent lands horizontally or vertically. You may assume all four edges of the grid are all surrounded by water.
On an infinite plane, a robot initially stands at (0, 0) and faces north. The robot can receive one of three instructions:
- “G”: go straight 1 unit;
- “L”: turn 90 degrees to the left;
- “R”: turn 90 degrees to the right.
The robot performs the instructions given in order, and repeats them forever.
Return true if and only if there exists a circle in the plane such that the robot never leaves the circle.
1519. Number of Nodes in the Sub-Tree With the Same Label
Given a tree (i.e. a connected, undirected graph that has no cycles) consisting of n nodes numbered from 0 to n - 1 and exactly n - 1 edges. The root of the tree is the node 0, and each node of the tree has a label which is a lower-case character given in the string labels (i.e. The node with the number i has the label labels[i]).
The edges array is given on the form edges[i] = [ai, bi], which means there is an edge between nodes ai and bi in the tree.
Return an array of size n where ans[i] is the number of nodes in the subtree of the ith node which have the same label as node i.
A subtree of a tree T is the tree consisting of a node in T and all of its descendant nodes.
Given an m x n grid of characters board and a string word, return true if word exists in the grid.
The word can be constructed from letters of sequentially adjacent cells, where adjacent cells are horizontally or vertically neighboring. The same letter cell may not be used more than once.
307. Range Sum Query - Mutable
Given an integer array nums, handle multiple queries of the following types:
- Update the value of an element in nums.
- Calculate the sum of the elements of nums between indices left and right inclusive where left <= right.
Implement the NumArray class:
- NumArray(int[] nums) Initializes the object with the integer array nums.
- void update(int index, int val) Updates the value of nums[index] to be val.
- int sumRange(int left, int right) Returns the sum of the elements of nums between indices left and right inclusive (i.e. nums[left] + nums[left + 1] + … + nums[right]).
1567. Maximum Length of Subarray With Positive Product
Given an array of integers nums, find the maximum length of a subarray where the product of all its elements is positive.
A subarray of an array is a consecutive sequence of zero or more values taken out of that array.
Return the maximum length of a subarray with positive product.
842. Split Array into Fibonacci Sequence
Given a string S of digits, such as S = “123456579”, we can split it into a Fibonacci-like sequence [123, 456, 579].
Formally, a Fibonacci-like sequence is a list F of non-negative integers such that:
- 0 <= F[i] <= 2^31 - 1, (that is, each integer fits a 32-bit signed integer type);
- F.length >= 3;
- and F[i] + F[i+1] = F[i+2] for all 0 <= i < F.length - 2.
Also, note that when splitting the string into pieces, each piece must not have extra leading zeroes, except if the piece is the number 0 itself.
Return any Fibonacci-like sequence split from S, or return [] if it cannot be done.
Given an integer n (in base 10) and a base k, return the sum of the digits of n after converting n from base 10 to base k.
After converting, each digit should be interpreted as a base 10 number, and the sum should be returned in base 10.
1839. Longest Substring Of All Vowels in Order
A string is considered beautiful if it satisfies the following conditions:
- Each of the 5 English vowels (‘a’, ‘e’, ‘i’, ‘o’, ‘u’) must appear at least once in it.
- The letters must be sorted in alphabetical order (i.e. all ‘a’s before ‘e’s, all ‘e’s before ‘i’s, etc.).
For example, strings “aeiou” and “aaaaaaeiiiioou” are considered beautiful, but “uaeio”, “aeoiu”, and “aaaeeeooo” are not beautiful.
Given a string word consisting of English vowels, return the length of the longest beautiful substring of word. If no such substring exists, return 0.
A substring is a contiguous sequence of characters in a string.