lxy的学习笔记

问题：Calculate the sum of two integers a and b, but you are not allowed to use the operator + and -.Example:Given a = 1 and b = 2, return 3.分析：这里要求我们不能用加法、减法等运算符来实现加法运算。这里应该使用位运算来实现加法运算，实际上，这也是计算机CPU内部实

题目：Implement pow(x, n).分析： 题目很短，就是实现pow求幂函数，直觉告诉我，这个题目的主要要求是降低程序的时间复杂度，果不其然，提交了一份带有while循环复杂度是O(n)的代码，返回“Time Limit Exceed“的错误，初次提交代码：class Solution {public: double myPow(double x, int n) {

Given a binary tree and a sum, find all root-to-leaf paths where each path's sum equals the given sum.For example:Given the below binary tree and sum = 22, 5 / \

题目：Given a binary tree, find its minimum depth.The minimum depth is the number of nodes along the shortest path from the root node down to the nearest leaf node.分析： 要得出二叉树中所有从根到叶子节点路径中，经过结点最少路径上的节点数。

题目：Given a binary tree and a sum, determine if the tree has a root-to-leaf path such that adding up all the values along the path equals the given sum.For example:Given the below binary tree and sum =

题目：Given a binary tree, return all root-to-leaf paths.For example, given the following binary tree: 1 / \2 3 \ 5All root-to-leaf paths are:["1->2->5", "1->3"]分析：让你对一棵树进行遍历，找出所有从跟节点到到叶子节点的

题目：Given a binary tree, check whether it is a mirror of itself (ie, symmetric around its center).For example, this binary tree is symmetric: 1 / \ 2 2 / \ / \3 4 4 3But the following is

题目：Find the contiguous subarray within an array (containing at least one number) which has the largest sum.For example, given the array [−2,1,−3,4,−1,2,1,−5,4],the contiguous subarray [4,−1,2,1] has t

题目：The string "PAYPALISHIRING" is written in a zigzag pattern on a given number of rows like this: (you may want to display this pattern in a fixed font for better legibility)P A H NA P L S I I

题目Given an array of numbers nums, in which exactly two elements appear only once and all the other elements appear exactly twice. Find the two elements that appear only once.For example:Given nums = [1

问题：Given a non-negative number represented as an array of digits, plus one to the number.The digits are stored such that the most significant digit is at the head of the list.解决：public class Solution {

Given an array nums, write a function to move all 0’s to the end of it while maintaining the relative order of the non-zero elements.For example, given nums = [0, 1, 0, 3, 12], after calling your funct