Given an array S of n integers, are there elements a, b, c, and d in S such that a + b + c + d = target? Find all unique quadruplets in the array which gives the sum of target.
Note: The solution set must not contain duplicate quadruplets.
For example, given array S = [1, 0, -1, 0, -2, 2], and target = 0. A solution set is: [ [-1, 0, 0, 1], [-2, -1, 1, 2], [-2, 0, 0, 2] ]
在给定数组中找出“和为 target 的四个数”的所有解。
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 an array S of n integers, are there elements a, b, c in S such that a + b + c = 0? Find all unique triplets in the array which gives the sum of zero.
Note: The solution set must not contain duplicate triplets.
For example, given array S = [-1, 0, 1, 2, -1, -4], A solution set is: [ [-1, 0, 1], [-1, -1, 2] ]
在给定数组中找出“和为0的三个数”的所有解。
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:
Given n non-negative integers a1, a2, …, an, where each represents a point at coordinate (i, ai). n vertical lines are drawn such that the two endpoints of line i is at (i, ai) and (i, 0). Find two lines, which together with x-axis forms a container, such that the container contains the most water. Note: You may not slant the container and n is at least 2.
给出n个点，它们与X轴有n条垂线，每两条垂线与X轴形成的U型容器，找出最大“容积”(面积）
The n-queens puzzle is the problem of placing n queens on an n×n chessboard such that no two queens attack each other.
Given an integer n, return all distinct solutions to the n-queens puzzle.
Each solution contains a distinct board configuration of the n-queens' placement, where
'Q'and'.'both indicate a queen and an empty space respectively.
Given n non-negative integers representing an elevation map where the width of each bar is 1, compute how >much water it is able to trap after raining.
For example, Given
[0,1,0,2,1,0,1,3,2,1,2,1], return6.
The above elevation map is represented by array [0,1,0,2,1,0,1,3,2,1,2,1]. In this case, 6 units of rain water (blue section) are being trapped. Thanks Marcos for contributing this image!
