LadyFeline的自养地

原型：Determine whether an integer is a palindrome. Do this without extra space.click to show spoilers.Some hints:Could negative integers be palindromes? (ie, -1)If you are thinking of conver

原题：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

原题：Given preorder and inorder traversal of a tree, construct the binary tree.Note:You may assume that duplicates do not exist in the tree.思路：通过先序我们可以找到根节点，再到中序序列中去找到根节点，根节点的左边便为左子树，右边为右子

原题：Given an array of integers, every element appears three times except for one. Find that single one.Note:Your algorithm should have a linear runtime complexity. Could you implement it withou

原题：Given inorder and postorder traversal of a tree, construct the binary tree.Note:You may assume that duplicates do not exist in the tree.思路：和上一题一样，后续我们可以通过最后一个值得到根的值，同样可以通过定位根的值得到左右子树的

原题：Sort a linked list using insertion sort.知识把

原题：Reverse digits of an integer.Example1: x = 123, return 321Example2: x = -123, return -321zhedao

原题：Given a binary tree, find its maximum depth.The maximum depth is the number of nodes along the longest path from the root node down to the farthest leaf node.

原题：Given two binary trees, write a function to check if they are equal or not.Two binary trees are considered equal if they are structurally identical and the nodes have the same value.

为这个问题纠结了好久表示自己太菜了。这个问题主要应该是二进制思想的英语

原题：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

原题：Given a binary tree, return the preorder traversal of its nodes' values.For example:Given binary tree {1,#,2,3}, 1 \ 2 / 3return [1,2,3].Note: Recursive solutio

原题：Divide two integers without using multiplication, division and mod operator.思路： 记录除数与被除数的符号跑

原题：Given a binary tree, determine if it is a valid binary search tree (BST).Assume a BST is defined as follows:The left subtree of a node contains only nodes with keys less than the node's k

原题：Given a linked list, determine if it has a cycle in it.Follow up:Can you solve it without using extra space?

原题：Say you have an array for which the ith element is the price of a given stock on dayi.If you were only permitted to complete at most one transaction (ie, buy one and sell one share of the s

原题：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.思路：深度优先

原题：Given a binary tree containing digits from 0-9 only, each root-to-leaf path could represent a number.An example is the root-to-leaf path 1->2->3 which represents the number123.Find the to

原题：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.思路：

原题：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 / \

原题：Given an array where elements are sorted in ascending order, convert it to a height balanced BST.【复习时间】：平衡二叉树（Balanced Binary Tree）具有以下性质：它是一棵空树或它的左右两个子树的高度差的绝对值不超过1，并且左右两个子树都是一棵平衡二叉树。常用算

Reverse a singly linked list.解析：/** * Definition for singly-linked list. * struct ListNode { * int val; * ListNode *next; * ListNode(int x) : val(x), next(NULL) {} * }; */class

Rotate an array of n elements to the right by k steps.For example, with n = 7 and k = 3, the array [1,2,3,4,5,6,7] is rotated to [5,6,7,1,2,3,4].class Solution {public: void rotate(int n

原题：Merge k sorted linked lists and return it as one sorted list. Analyze and describe its complexity.思路：两条两条地合并。时间复杂度为O（n），n为所有链表节点和。代码：/** * Definition for singly-linked list. * struct List

原题：Implement pow(x, n).思路：递归计算pow。class Solution {public: double pow(double x, int n) { long long int mid = n/2; int d = n%2; if(n==0) return 1; if(n==1) return

原题：Implement int sqrt(int x).Compute and return the square root of x.==============================以下为引用====================================牛顿迭代法   为了方便理解，就先以本题为例：   计算x2 = n的解，令f(

原题：Given a singly linked list where elements are sorted in ascending order, convert it to a height balanced BST.思路：和处理数组的思想类似，用递归。代码：

原题：Write a function to find the longest common prefix string amongst an array of strings.思路：pre赋给第一个strs值

原题：Determine if a Sudoku is valid, according to: Sudoku Puzzles - The Rules.The Sudoku board could be partially filled, where empty cells are filled with the character'.'.A partially f

原题：Say you have an array for which the ith element is the price of a given stock on dayi.If you were only permitted to complete at most one transaction (ie, buy one and sell one share of the s

原题：Evaluate the value of an arithmetic expression in Reverse Polish Notation.Valid operators are +, -, *, /. Each operand may be an integer or another expression.Some examples: ["2", "1",

原题：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 fo

原题：Given n, generate all structurally unique BST's (binary search trees) that store values 1...n.For example,Given n = 3, your program should return all 5 unique BST's shown below. 1

原题：Follow up for problem "Populating Next Right Pointers in Each Node".What if the given tree could be any binary tree? Would your previous solution still work?Note:You may only use consta

原题：Given two binary strings, return their sum (also a binary string).For example,a = "11"b = "1"Return "100".

原题 ：Say you have an array for which the ith element is the price of a given stock on day i.Design an algorithm to find the maximum profit. You may complete as many transactions as you like (

原题：Given an input string, reverse the string word by word.For example,Given s = "the sky is blue",return "blue is sky the".Clarification:What constitutes a word?A sequence of non-s

原题：Given a linked list, return the node where the cycle begins. If there is no cycle, returnnull.Follow up:Can you solve it without using extra space?先上代码：/** * Definition for singly-

原题：Follow up for "Remove Duplicates":What if duplicates are allowed at most twice?For example,Given sorted array A = [1,1,1,2,2,3],Your function should return length = 5, and A is now [1,1

原题：Given an index k, return the kth row of the Pascal's triangle.For example, given k = 3,Return [1,3,3,1].Note:Could you optimize your algorithm to use only O(k) extra space?思路：哟