[链接]MediumGoogle, Uber, Amazon, Twitch {代码...}

[链接]HardGoogle, Amazon第一种解法使用BFS {代码...} 第二种解法，DPdp[target] 表示行驶长度为target的距离需要的最小指示个数。dp[target]有两种可能：target刚好是由"AAA...A"一共n步到达，也就是一路加速，那么这种走法就是最优选择。如果不是上述情况，就有多种可能： a.第一次冲过target的时候进行'R'操作，然后...

字符串转整数 字符串开头可能有很多空格，忽略之，直到找到第一个不是空格的字符。 第一个非空格字符可能是加号，减号，表示正数或负数。 继续向后碰到0-9就解析，碰到其他字符就终止。 若第一段连续数字为空，返回0. 如果整数大于Integer.MAX_VALUE，返回MAX_VALUE；若小于Integer.MIN_VALUE，返回MIN_VALUE。 {代码...}

Given an array arr of positive integers, consider all binary trees such that:

You have 4 cards each containing a number from 1 to 9. You need to judge whether they could operated through *, /, +, -, (, )to get the value of 24.

Given a matrix consists of 0 and 1, find the distance of the nearest 0 for each cell.

There is a fence with n posts, each post can be painted with one of the k colors.

A strobogrammatic number is a number that looks the same when rotated 180 degrees (looked at upside down).

Given an array of n integers where n > 1, nums, return an array output such that output[i] is equal to the product of all the elements of nums except nums[i].Solve it without division and in O(n).

Given a set of candidate numbers (C) (without duplicates) and a target number (T), find all unique combinations in C where the candidate numbers sums to T. The same repeated number may be chosen from C unlimited number of times.例如: [2, 3, 6, 7] and target 7