Given an integer num, repeatedly add all its digits until the result has only one digit, and return it.
Given an integer num, repeatedly add all its digits until the result has only one digit, and return it.
You are given an integer array nums and an integer target.
You want to build an expression out of nums by adding one of the symbols ‘+’ and ‘-‘ before each integer in nums and then concatenate all the integers.
- For example, if nums = [2, 1], you can add a ‘+’ before 2 and a ‘-‘ before 1 and concatenate them to build the expression “+2-1”.
Return the number of different expressions that you can build, which evaluates to target.
Given the head of a linked list, return the list after sorting it in ascending order.
Write an efficient algorithm that searches for a value target in an m x n integer matrix matrix. This matrix has the following properties:
- Integers in each row are sorted in ascending from left to right.
- Integers in each column are sorted in ascending from top to bottom.
Given an array nums with n objects colored red, white, or blue, sort them in-place so that objects of the same color are adjacent, with the colors in the order red, white, and blue.
We will use the integers 0, 1, and 2 to represent the color red, white, and blue, respectively.
You must solve this problem without using the library’s sort function.
Given an m x n integer matrix matrix, if an element is 0, set its entire row and column to 0’s, and return the matrix.
You must do it in place.
295. Find Median from Data Stream
The median is the middle value in an ordered integer list. If the size of the list is even, there is no middle value and the median is the mean of the two middle values.
- For example, for arr = [2,3,4], the median is 3.
- For example, for arr = [2,3], the median is (2 + 3) / 2 = 2.5.
Implement the MedianFinder class:
- MedianFinder() initializes the MedianFinder object.
- void addNum(int num) adds the integer num from the data stream to the data structure.
- double findMedian() returns the median of all elements so far. Answers within 10-5 of the actual answer will be accepted.
You are given an array of integers nums, there is a sliding window of size k which is moving from the very left of the array to the very right. You can only see the k numbers in the window. Each time the sliding window moves right by one position.
Return the max sliding window.
The DNA sequence is composed of a series of nucleotides abbreviated as ‘A’, ‘C’, ‘G’, and ‘T’.
- For example, “ACGAATTCCG” is a DNA sequence.
When studying DNA, it is useful to identify repeated sequences within the DNA.
Given a string s that represents a DNA sequence, return all the 10-letter-long sequences (substrings) that occur more than once in a DNA molecule. 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.