Alex and Lee play a game with piles of stones. There are an even number of piles arranged in a row, and each pile has a positive integer number of stones piles[i].
The objective of the game is to end with the most stones. The total number of stones is odd, so there are no ties.
Alex and Lee take turns, with Alex starting first. Each turn, a player takes the entire pile of stones from either the beginning or the end of the row. This continues until there are no more piles left, at which point the person with the most stones wins.
Assuming Alex and Lee play optimally, return True if and only if Alex wins the game.

Example 1:
Input: [5,3,4,5]
Output: true
Explanation:
Alex starts first, and can only take the first 5 or the last 5.
Say he takes the first 5, so that the row becomes [3, 4, 5].
If Lee takes 3, then the board is [4, 5], and Alex takes 5 to win with 10 points.
If Lee takes the last 5, then the board is [3, 4], and Alex takes 4 to win with 9 points.
This demonstrated that taking the first 5 was a winning move for Alex, so we return true.

A positive integer is magical if it is divisible by either A or B.
Return the N-th magical number. Since the answer may be very large, return it modulo 10^9 + 7.

Example 1:
Input: N = 1, A = 2, B = 3
Output: 2

Koko loves to eat bananas. There are N piles of bananas, the i-th pile has piles[i] bananas. The guards have gone and will come back in H hours.
Koko can decide her bananas-per-hour eating speed of K. Each hour, she chooses some pile of bananas, and eats K bananas from that pile. If the pile has less than K bananas, she eats all of them instead, and won’t eat any more bananas during this hour.
Koko likes to eat slowly, but still wants to finish eating all the bananas before the guards come back.
Return the minimum integer K such that she can eat all the bananas within H hours.

Example 1:
Input: piles = [3,6,7,11], H = 8
Output: 4

A robot on an infinite grid starts at point (0, 0) and faces north. The robot can receive one of three possible types of commands:
-2: turn left 90 degrees
-1: turn right 90 degrees
1 <= x <= 9: move forward x units
Some of the grid squares are obstacles.
The i-th obstacle is at grid point (obstacles[i][0], obstacles[i][1])
If the robot would try to move onto them, the robot stays on the previous grid square instead (but still continues following the rest of the route.)
Return the square of the maximum Euclidean distance that the robot will be from the origin.

Example 1:
Input: commands = [4,-1,3], obstacles = []
Output: 25
Explanation: robot will go to (3, 4)

A sequence X_1, X_2, …, X_n is fibonacci-like if:
· n >= 3
· X_i + X_{i+1} = X_{i+2} for all i + 2 <= n
Given a strictly increasing array A of positive integers forming a sequence, find the length of the longest fibonacci-like subsequence of A. If one does not exist, return 0.
(Recall that a subsequence is derived from another sequence A by deleting any number of elements (including none) from A, without changing the order of the remaining elements. For example, [3, 5, 8] is a subsequence of [3, 4, 5, 6, 7, 8].)

Example 1:
Input: [1,2,3,4,5,6,7,8]
Output: 5
Explanation:
The longest subsequence that is fibonacci-like: [1,2,3,5,8].

给定两个单词 word1 和 word2，找到使得 word1 和 word2 相同所需的最小步数，每步可以删除任意一个字符串中的一个字符。

示例 1:
输入: “sea”, “eat”
输出: 2
解释: 第一步将”sea”变为”ea”，第二步将”eat”变为”ea”

给定一个整数数组，你需要寻找一个连续的子数组，如果对这个子数组进行升序排序，那么整个数组都会变为升序排序。
你找到的子数组应是最短的，请输出它的长度。

示例 1:
输入: [2, 6, 4, 8, 10, 9, 15]
输出: 5
解释: 你只需要对 [6, 4, 8, 10, 9] 进行升序排序，那么整个表都会变为升序排序。

给定一个 m × n 的网格和一个球。球的起始坐标为 (i,j) ，你可以将球移到相邻的单元格内，或者往上、下、左、右四个方向上移动使球穿过网格边界。但是，你最多可以移动N次。找出可以将球移出边界的路径数量。答案可能非常大，返回结果mod 1e9+7的值。

给定一个偶数长度的数组，其中不同的数字代表着不同种类的糖果，每一个数字代表一个糖果。你需要把这些糖果平均分给一个弟弟和一个妹妹。返回妹妹可以获得的最大糖果的种类数。

示例 1:
输入: candies = [1,1,2,2,3,3]
输出: 3
解析: 一共有三种种类的糖果，每一种都有两个。最优分配方案：妹妹获得[1,2,3],弟弟也获得[1,2,3]。这样使妹妹获得糖果的种类数最多。