Length of Last Word Given a string s consists of upper/lower-case alphabets and empty space characters ‘…

题目地址：https://leetcode-cn.com/probl…题目描述：给定一个二叉树（具有根结点 root）， 一个目标结点 target ，和一个整数值 K 。 返回到目标结点 target 距离…

  Roman numerals are represented by seven different symbols: I, V, X, L, C, …

  Initially, there is a Robot at position (0, 0). Given a sequence of its moves, judge if this robot make…

  You have 4 cards each containing a number from 1 to 9. You need to judge whether they could operated th…

The thief has found himself a new place for his thievery again. There is only one entrance to this area, calle…

  Given an array of characters, compress it in-place. The length after compression must always be sm…

题目描述 Given a string of numbers and operators, return all possible results from computing all the different pos…

Expression Add Operators Given a string that contains only digits 0-9 and a target value, return all possibili…

题目地址：https://leetcode-cn.com/probl…题目描述：给定一个二叉树，返回其节点值的锯齿形层次遍历。（即先从左往右，再从右往左进行下一层遍历，以此类推，层与层之间交替进行）。 解答：…

130. Surrounded Regions 题目 Given a 2D board containing 'X' and 'O' (the letter O), capture all regions surroun…

  In a 2D grid from (0, 0) to (N-1, N-1), every cell contains a 1, except those cells in t…