leetcode

LeetCode.001.Two Sum, leetcode.001.two Address: https://leetcode.com/problems/two-sum/ Question: Given an array and a target, if the sum of two numbers in the array is exactly the same as the target, their subscript is returned. Question: There are a lot of ideas. You can simply do this by sorting them first, then traversing each number, and searching for the other in binary mode. Because python come

Leetcode 1, leetcodeQuestion Given an array of integers, returnindicesof the two numbers such that they add up to a specific target.You may assume that each input would haveexactlyone solution.Example:Given nums = [2, 7, 11, 15], target = 9,Because nums[0] + nums[1] = 2 + 7 = 9,return [0, 1].Solution Public int [] TwoSum (int [] nums, int target) {# region solution 1, brute force cracking method int [] newInt = null; for (int I = 0; I Solution on OJ:

[Leetcode-easy] String to Integer (atoi), leetcode-easyatoi Requirement: String> integer * 1. First, discard the space before the string.* 2. Then there may be positive and negative signs (note that only one is taken. If there are multiple positive and negative signs, this string cannot be converted and 0 is returned. For example, there is a "+-2" in the test case ").* 3. The string can contain 0 ~ If a non

LeetCode -- Same Tree, leetcode -- sametreeQuestion: 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.Solution: /*** Definition for binary tree * public class TreeNode {* int val; * TreeNode left; * TreeNode right; * TreeNode (int x) {val = x ;} *} */public class Solution

[LeetCode] Best Time to Buy and keep Stock IV, leetcode= Say you have an array for which Ith Element is the price of a given stock on day I . Design an algorithm to find the maximum profit. You may complete at most k transactions. Note:You may not engage in multiple transactions at the same time (ie, you must encrypt the stock before you buy again ).Solutions Use Dynamic Planning to solve the p

[LeetCode from zero to single row] No70.ClimbingStairs, leetcodeThis is an interesting question. First, let's look at the question: 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? There are three methods to implement this question (I think ): 1. recursion (corresponding code: climbStairs) If the stair has n layers, we rolled back to Th

LeetCode -- Permutation Sequence, leetcode The set[1,2,3,…,n]Contains a total of n! Unique permutations. By listing and labeling all of the permutations in order,We get the following sequence (ie, for n = 3 ): "123" "132" "213" "231" "312" "321" Given n and k, return the kth permutation sequence. Note: Given n will be between 1 and 9 inclusive. Original question link: https://oj.leetcode.com/proble

Leetcode -- Kth Smallest Element in a BST, leetcode Given a binary search tree, write a function kthSmallest to find the kth smallest element in it. Note:You may assume k is always valid, 1 ≤ k ≤ BST's total elements. Follow up:What if the BST is modified (insert/delete operations) often and you need to find the kth smallest frequently? How wocould you optimize the kthSmallest routine? Hint: Try to utilize

Leetcode-Maximum Gap, leetcode-maximum Given an unsorted array, find the maximum difference between the successive elements in its sorted form. Try to solve it in linear time/space. Return 0 if the array contains less than 2 elements. You may assume all elements in the array are non-negative integers and fit in the 32-bit signed integer range. Class Solution {public: int maximumGap (vector

Bitwise AND of Numbers Range -- LeetCode, leetcode Given a range [m, n] where 0 For example, given the range [5, 7], you shoshould return 4. Train of Thought: the first train of thought must start with bitwise AND from the first number, but the complexity is too high and new improvements are made. If there is a power of 2 in this range, from this point on, the power of the 2 is equal to n. If the power of

LeetCode | Best time to buy and keep stock 2, leetcode= Question: 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 your transactions as you like (ie, buy one and every one share of the stock multiple times ). however, you may not engage in multiple transactions at the same time (ie, you must wait

Leetcode notes: 4Sum, leetcode notes 4sum I. Description Ii. problem-solving skills On the surface, this question is very similar to 3Sum. In fact, we can use the same thinking and method. However, in this case, the time complexity is O (n ^ 3 ), the space complexity is O (1) and will time out. This question can also be used to calculate the sum of the next two numbers after sorting. In a hash table, the

[LeetCode-interview algorithm classic-Java implementation] [002-Add Two Numbers (Two Numbers in a single-chain table)], leetcode -- java [002-Add Two Numbers )]Original question You 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 numbers and return it as a linked list.Input: (2-> 4-> 3) + (5-

[Leetcode]-Maximum Depth of Binary Tree, leetcode-maximum 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. Hide Tags: Tree, Depth-first SearchQuestion: obtain the maximum depth in a binary tree. The root node is defined as 1 depth.Idea: recursion is also adoptedRecursive termination conditions:A:

[Leetcode]-Path Sum, leetcode-pathsum 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 = 22,5/\4 8//\11 13 4/\\7 2 1Return true, as there exist a root-to-leaf path 5-> 4-> 11-> 2 which sum is 22. Hide Tags: Tree, Depth-first SearchQuestion: Find out if the sum

Leetcode 22, leetcode Generate Parentheses Question:Given n pairs of parentheses, write a function to generate all combinations of well-formed parentheses.For example, given n = 3, a solution set is:"()", "() ()()" Question:Returns the logarithm of parentheses and any combination to find all strings that meet the matching principle of parentheses. Ideas:Just consider the rule. The rule is to ensu

LeetCode 97: Interleaving String staggered, flip String leetcode Blog reprint please note address: http://blog.csdn.net/SunliyMonkey/article/details/48165711Description Address: https://leetcode.com/problems/interleaving-string/Three strings S1 , S2 , S3 , Judge S3 Whether S1 , S2 In combination. Example: S1 = aabcc S2 = dbbca When S3 = aadbbcbcac R

LeetCode -- Reverse Words in a String, leetcode Given an input string, reverse the string word by word. For example,Given s = "the sky is blue ",Return "blue is sky ". Click to show clarification. Clarification:What constitutes a word?A sequence of non-space characters constitutes a word.Cocould the input string contain leading or trailing spaces?Yes. However, your reversed string shocould not contain leadi

Leetcode [110]-Balanced Binary Tree, leetcode-balanced 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 differ by more than 1. Determine whether a tree belongs to a balanced binary tree Determine the depth difference between the left and right nodes of the master no

Leetcode Note: Leetcode Letter Combinations of a Phone Number I. Description Given a digit string, return all possible letter combinations that the number coshould 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"]. Ii. Question Analysis The question is: press a letter on your ph