martinmateng的博客

Given an index k, return the kth row of the Pascal's triangle.For example, given k = 3,Return [1,3,3,1].思路:我们可以把这个pascal三角用二维数组来解决。a[i][0]=1,a[i][j]=a[i-1][j-1]+a[i-1][j]根据此递推式就可以得出a[i

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

Implement the following operations of a stack using queues.push(x) -- Push element x onto stack.pop() -- Removes the element on top of the stack.top() -- Get the top element.empty() -- Return whet

Given an array and a value, remove all instances of that value in place and return the new length.The order of elements can be changed. It doesn't matter what you leave beyond the new length. 

Given a binary tree, determine if it is height-balanced.For this problem, a height-balanced binary tree is defined as a binary tree in which the depth of the two subtrees of every node never diffe

Given an integer, write a function to determine if it is a power of two.思路：注意题意是判断一个数是不是2的幂。一直除以2，如果除不尽就不是2的幂，当等于1的时候，就返回true；代码如下(已通过leetcode)public class Solution {   public boolean isPowerO

Implement the following operations of a queue using stacks.push(x) -- Push element x to the back of queue.pop() -- Removes the element from in front of queue.peek() -- Get the front element.empty(

Write an algorithm to determine if a number is "happy".A happy number is a number defined by the following process: Starting with any positive integer, replace the number by the sum of the squares

Reverse a singly linked list.思路:这个应该都会，只是简单的链表转置。就是设置三个指针一个p,一个pleft,一个pright.代码如下(已通过leetcode)public class Solution {   public ListNode reverseList(ListNode head) {       ListNode p=head;

Write a function that takes an unsigned integer and returns the number of ’1' bits it has (also known as theHamming weight).For example, the 32-bit integer ’11' has binary representation 0000000

Given an array S of n integers, find three integers in S such that the sum is closest to a given number, target. Return the sum of the three integers. You may assume that each input would have exact

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:Elements in a triplet (a,b,c

Write a function to find the longest common prefix string amongst an array of strings.思路1:本题是要找一个字符串数组的最长公共前缀。首先求出最短字符串的长度，然后从0到最短字符串长度遍历每个字符串，找到最长的公共前缀代码如下(已通过leetcode)public class Solution {

Related to question Excel Sheet Column TitleGiven a column title as appear in an Excel sheet, return its corresponding column number.For example: A -> 1 B -> 2 C -> 3 ...

You are climbing a stair case. It takes n steps to reach to the top.Each time you can either climb 1 or 2 steps. In how many distinct ways can you climb to the top?思路:先计算出几个特殊情况的楼梯数目所需的步数的情况，

Given an array of integers, find if the array contains any duplicates. Your function should return true if any value appears at least twice in the array, and it should return false if every element

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 you

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.思路：本题是比较两棵

Write a function to delete a node (except the tail) in a singly linked list, given only access to that node.Supposed the linked list is 1 -> 2 -> 3 -> 4 and you are given the third node with val

Given a non-negative integer num, repeatedly add all its digits until the result has only one digit.For example:Given num = 38, the process is like: 3 + 8 = 11, 1 + 1 = 2. Since 2 has on

You are playing the following Nim Game with your friend: There is a heap of stones on the table, each time one of you take turns to remove 1 to 3 stones. The one who removes the last stone will be the

Given a roman numeral, convert it to an integer.Input is guaranteed to be within the range from 1 to 3999.思路：从前向后遍历这个字符串如果当前值等于前一个值 则用一个临时变量存储当前的值 如III=3；如果当前值比前一个值大 则这个临时变量存储的值应该为当前值减

Given an integer, convert it to a roman numeral.Input is guaranteed to be within the range from 1 to 3999.思路:首先先把num按照个位十位百位千位拆分，然后对每一位上的数字按照roman to integer的对应表格，转化为对应的roman，然后就所有转化的再拼起来就是所求的

'.' Matches any single character.'*' Matches zero or more of the preceding element.The matching should cover the entire input string (not partial).The function prototype should be:bool isMatch(c

Implement atoi to convert a string to an integer.思路：本题的题目本身比较简单，但是case非常的多比如:1  "+"2  " +-12"3  "  0012a45"4 溢出等等，本题的重点就在于处理这些case。下面代码(已经通过lootcode)今天就刷到这，保持基本每天4题的速度public class

Reverse digits of an integer.Example1: x = 123, return 321Example2: x = -123, return -321思路：题目本身简单的不能再简单了，但是其中有一个边界问题，也是这个题目存在的道理，就是当输出的整数没有越界，而转置之后的整数可能会越界。比如 1534236469本身并没有越界，而转置之后就96463243

Given a string, find the length of the longest substring without repeating characters. For example, the longest substring without repeating letters for "abcabcbb" is "abc", which the length is 3. Fo

There are two sorted arrays nums1 and nums2 of size m and n respectively. Find the median of the two sorted arrays. The overall run time complexity should be O(log (m+n)).思路1：本题毫无疑问第一反应肯定是使用递归求解。此

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

Given a sorted linked list, delete all duplicates such that each element appear only once.For example,Given 1->1->2, return 1->2.Given 1->1->2->3->3, return 1->2->3.思路：就是一个普通的链表操作，设置两个指针，p

Given two strings s and t, write a function to determine if t is an anagram of s.For example,s = "anagram", t = "nagaram", return true.s = "rat", t = "car", return false.Note:You may ass

Determine whether an integer is a palindrome. Do this without extra space.思路:就是简单的判断是不是回文数，在头尾设置两个指针i和j，判断是不是一直相等就行。本题的关键是不要有额外的空间，所以创建一个数组就是不可行的了，我是将其转换成了字符串。代码如下，已通过(leetcode)扯淡几句：由于在机房没带耳机，没法学别

Add Two NumbersYou are given two linked lists representing two non-negative numbers. The digits are stored in reverse order and each of their nodes contain a single digit.  Add the two num

Given an array of integers, find two numbers such that they add up to a specific target number.The function twoSum should return indices of the two numbers such that they add up to the target, whe

Given a sorted array, remove the duplicates in place such that each element appear only once and return the new length.Do not allocate extra space for another array, you must do this in place with

Given a binary tree, return the bottom-up level order traversal of its nodes' values. (ie, from left to right, level by level from leaf to root).For example:Given binary tree {3,9,20,#,#,15,7},

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 f

Given a binary search tree (BST), find the lowest common ancestor (LCA) of two given nodes in the BST.According to the definition of LCA on Wikipedia: “The lowest common ancestor is defined betw

Invert a binary tree. 4 / \ 2 7 / \ / \1 3 6 9to 4 / \ 7 2 / \ / \9 6 3 1Trivia:This problem was inspired by this original tweet by Max Howe

Given a string S, find the longest palindromic substring in S. You may assume that the maximum length of S is 1000, and there exists one unique longest palindromic substring.思路:1 本题有两种想法，第一种是找