Each time you can either climb 1 or 2 steps. In how many distinct ways can you climb to the top?

1. 题目 Implement int sqrt(int x). Compute and return the square root of x. 注：对于5，6，7，8等都返回2. 2. 思路 用牛顿开方法计算。原理： [链接] 3. 代码 {代码...}

1. 题目 Given two binary strings, return their sum (also a binary string). For example,a = "11"b = "1"Return "100". 2. 思路 从后往前相加和进位。 3. 代码 {代码...}

Given a non-negative number represented as an array of digits, plus one to the number.

Some examples:"0" => true" 0.1 " => true"abc" => false"1 a" => false"2e10" => trueNote: It is intended for the problem statement to be ambiguous. You should gather all requirements up front before implementing one.

Given a m x n grid filled with non-negative numbers, find a path from top left to bottom right which minimizes the sum of all numbers along its path.

Now consider if some obstacles are added to the grids. How many unique paths would there be?

A robot is located at the top-left corner of a m x n grid (marked 'Start' in the diagram below).

Given a list, rotate the list to the right by k places, where k is non-negative.

By listing and labeling all of the permutations in order,We get the following sequence (ie, for n = 3):

Given an integer n, generate a square matrix filled with elements from 1 to n2 in spiral order.

Given a string s consists of upper/lower-case alphabets and empty space characters ' ', return the length of last word in the string.

Given a set of non-overlapping intervals, insert a new interval into the intervals (merge if necessary).

For example,Given [1,3],[2,6],[8,10],[15,18],return [1,6],[8,10],[15,18].

Given an array of non-negative integers, you are initially positioned at the first index of the array.

Given a matrix of m x n elements (m rows, n columns), return all elements of the matrix in spiral order.

Find the contiguous subarray within an array (containing at least one number) which has the largest sum.

Now, instead outputting board configurations, return the total number of distinct solutions.

The n-queens puzzle is the problem of placing n queens on an n×n chessboard such that no two queens attack each other.

n如果是numeric_limits<int>::min()的值，如果下面的代码中i用int表示，i最后会越界，导致死循环，因为i会变为负数，abs_n会变大，而之后i变为0，abs_n不会再减小，于是就死循环了。

For example, given: ["eat", "tea", "tan", "ate", "nat", "bat"], Return:

每次旋转最外层的一圈正方形的边，迭代N/2次逐层的将整个都旋转一次。每个正方形的旋转是，用顶边遍历边的每一个节点（最后一个节点除外）,将当前正边型的以当前遍历点为左上顶点的内正边型的四个顶点进行旋转。

Given a collection of numbers that might contain duplicates, return all possible unique permutations.

Given a collection of distinct numbers, return all possible permutations.

Given an array of non-negative integers, you are initially positioned at the first index of the array.

'?' Matches any single character.'*' Matches any sequence of characters (including the empty sequence).

Given two numbers represented as strings, return multiplication of the numbers as a string.

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.

Given an unsorted integer array, find the first missing positive integer.

Given a collection of candidate numbers (C) and a target number (T), find all unique combinations in C where the candidate numbers sums to T.