songxt

描述：Initially, there is a Robot at position (0, 0). Given a sequence of its moves, judge if this robot makes a circle, which means it moves back to the original place. The move sequence is represente...

描述：Given a string containing just the characters ‘(’, ‘)’, ‘{’, ‘}’, ‘[’ and ‘]’, determine if the input string is valid. An input string is valid if: Open brackets must be closed by the same type o...

描述：You’re given strings J representing the types of stones that are jewels, and S representing the stones you have. Each character in S is a type of stone you have. You want to know how many of the...

描述：Given a string, you need to reverse the order of characters in each word within a sentence while still preserving whitespace and initial word order. Example 1: Input: “Let’s take LeetCode contes...

描述： Every email consists of a local name and a domain name, separated by the @ sign. For example, in alice@leetcode.com, alice is the local name, and leetcode.com is the domain name. Besides lowercas...

描述：International Morse Code defines a standard encoding where each letter is mapped to a series of dots and dashes, as follows: “a” maps to “.-“, “b” maps to “-…”, “c” maps to “-.-.”, and so on. Fo...

描述： Implement function ToLowerCase() that has a string parameter str, and returns the same string in lowercase. Example 1: Input: “Hello” Output: “hello” Example 2: Example 2: Inpu...

描述：A sentence S is given, composed of words separated by spaces. Each word consists of lowercase and uppercase letters only. We would like to convert the sentence to “Goat Latin” (a made-up language...

描述：Write a function that takes a string as input and returns the string reversed. Example: Given s = “hello”, return “olleh”. 分析：转换字符串的方向，水题 思路一：利用for循环从后向前读取。 class Solution { public: s...

描述：Write a function to find the longest common prefix string amongst an array of strings. If there is no common prefix, return an empty string “”. Example 1: Input: [“flower”,“flow”,“flight”] Outpu...