Given a string s consists of upper/lower-case alphabets and empty space characters ' ‘, return the length of last word in the string.
If the last word does not exist, return 0.
Note: A word is defined as a character sequence consists of non-space characters only.
Example:
Input: "Hello World" Output: 5
求给出的字符串中最后一个单词的长度。
Given two non-negative integers
num1andnum2represented as strings, return the product ofnum1andnum2, also represented as a string.Example 1:
Input: num1 = “2”, num2 = “3” Output: “6”
Example 2:
Input: num1 = “123”, num2 = “456” Output: “56088”
将两个字符串表示的数字相乘（大数相乘）。
Given a string containing just the characters
'('and')', find the length of the longest valid (well-formed) parentheses substring. Example 1:Input: "(()" Output: 2 Explanation: The longest valid parentheses substring is "()"
输出最长的左右括号匹配的子串长度
Given n pairs of parentheses, write a function to generate all combinations of well-formed parentheses.
For example, given n = 3, a solution set is:
[ "((()))", "(()())", "(())()", "()(())", "()()()" ]
给出n组括号，生成所有正确的匹配组合
Given a string containing just the characters
'(',')','{','}','['and']', determine if the input string is valid. The brackets must close in the correct order,"()"and"()[]{}"are all valid but"(]"and"([)]"are not.
给出包含三种括号的字符串，验证括号是否左右匹配
Letter Combinations of a Phone Number
Given a digit string, return all possible letter combinations that the number could represent.
A mapping of digit to letters (just like on the telephone buttons) is given below.
Input: Digit string "23" Output: ["ad", "ae", "af", "bd", "be", "bf", "cd", "ce", "cf"].
输入九宫格输入法数字，输出对应的所有字母组合
Given a roman numeral, convert it to an integer. Input is guaranteed to be within the range from 1 to 3999.
将罗马数字转换成整型。
Given an integer, convert it to a roman numeral. Input is guaranteed to be within the range from 1 to 3999.
将整型转换成罗马数字形式:
