774. Minimize Max Distance to Gas Station

You are given an integer array stations that represents the positions of the gas stations on the x-axis. You are also given an integer k.

You should add k new gas stations. You can add the stations anywhere on the x-axis, and not necessarily on an integer position.

Let penalty() be the maximum distance between adjacent gas stations after adding the k new stations.

Return the smallest possible value of penalty(). Answers within 10-6 of the actual answer will be accepted.

568. Maximum Vacation Days

LeetCode wants to give one of its best employees the option to travel among n cities to collect algorithm problems. But all work and no play makes Jack a dull boy, you could take vacations in some particular cities and weeks. Your job is to schedule the traveling to maximize the number of vacation days you could take, but there are certain rules and restrictions you need to follow.

Rules and restrictions:

1. You can only travel among n cities, represented by indexes from 0 to n - 1. Initially, you are in the city indexed 0 on Monday.
2. The cities are connected by flights. The flights are represented as an n x n matrix (not necessarily symmetrical), called flights representing the airline status from the city i to the city j. If there is no flight from the city i to the city j, flights[i][j] == 0; Otherwise, flights[i][j] == 1. Also, flights[i][i] == 0 for all i.
3. You totally have k weeks (each week has seven days) to travel. You can only take flights at most once per day and can only take flights on each week’s Monday morning. Since flight time is so short, we do not consider the impact of flight time.
4. For each city, you can only have restricted vacation days in different weeks, given an n x k matrix called days representing this relationship. For the value of days[i][j], it represents the maximum days you could take a vacation in the city i in the week j.
5. You could stay in a city beyond the number of vacation days, but you should work on the extra days, which will not be counted as vacation days.
6. If you fly from city A to city B and take the vacation on that day, the deduction towards vacation days will count towards the vacation days of city B in that week.
7. We do not consider the impact of flight hours on the calculation of vacation days.

Given the two matrices flights and days, return the maximum vacation days you could take during k weeks.

471. Encode String with Shortest Length

Given a string s, encode the string such that its encoded length is the shortest.

The encoding rule is: k[encoded_string], where the encoded_string inside the square brackets is being repeated exactly k times. k should be a positive integer.

If an encoding process does not make the string shorter, then do not encode it. If there are several solutions, return any of them.

1231. Divide Chocolate

You have one chocolate bar that consists of some chunks. Each chunk has its own sweetness given by the array sweetness.

You want to share the chocolate with your k friends so you start cutting the chocolate bar into k + 1 pieces using k cuts, each piece consists of some consecutive chunks.

Being generous, you will eat the piece with the minimum total sweetness and give the other pieces to your friends.

Find the maximum total sweetness of the piece you can get by cutting the chocolate bar optimally.

1100. Find K-Length Substrings With No Repeated Characters

Given a string s and an integer k, return the number of substrings in s of length k with no repeated characters.

733. Flood Fill

An image is represented by an m x n integer grid image where image[i][j] represents the pixel value of the image.

You are also given three integers sr, sc, and newColor. You should perform a flood fill on the image starting from the pixel image[sr][sc].

To perform a flood fill, consider the starting pixel, plus any pixels connected 4-directionally to the starting pixel of the same color as the starting pixel, plus any pixels connected 4-directionally to those pixels (also with the same color), and so on. Replace the color of all of the aforementioned pixels with newColor.

Return the modified image after performing the flood fill.

203. Remove Linked List Elements

Given the head of a linked list and an integer val, remove all the nodes of the linked list that has Node.val == val, and return the new head.

21. Merge Two Sorted Lists

You are given the heads of two sorted linked lists list1 and list2.

Merge the two lists in a one sorted list. The list should be made by splicing together the nodes of the first two lists.

Return the head of the merged linked list.

136. Single Number

Given a non-empty array of integers nums, every element appears twice except for one. Find that single one.

You must implement a solution with a linear runtime complexity and use only constant extra space.

947. Most Stones Removed with Same Row or Column

On a 2D plane, we place n stones at some integer coordinate points. Each coordinate point may have at most one stone.

A stone can be removed if it shares either the same row or the same column as another stone that has not been removed.

Given an array stones of length n where stones[i] = [xi, yi] represents the location of the ith stone, return the largest possible number of stones that can be removed.