104.MaximumDepthofBinaryTreeEasyGivenabinarytree,finditsmaximumdepth.Themaximumdepthisthenumberofnodesalongthelongestpathfromtherootnodedowntothefarthestleafnod...

Givenabinarytree,returnthelevelordertraversalofitsnodes'values.(ie,fromlefttoright,levelbylevel).Forexample:Givenbinarytree[3,9,20,null,null,15,7],3/920/157&nbs...

https://www.geeksforgeeks.org/bfs-vs-dfs-binary-tree/WhatareBFSandDFSforBinaryTree?ATreeistypicallytraversedintwoways:BreadthFirstTraversal(OrLevelOrderTraversa...

https://leetcode.com/problems/convert-sorted-array-to-binary-search-tree/Givenanarraywhereelementsaresortedinascendingorder,convertittoaheightbalancedBST.Forthi...

Givenabinarytree,finditsminimumdepth.Theminimumdepthisthenumberofnodesalongtheshortestpathfromtherootnodedowntothenearestleafnode.Note: Aleafisanodewithnoc...

Givenabinarytree,determineifitisheight-balanced.Forthisproblem,aheight-balancedbinarytreeisdefinedas:/abinarytreeinwhichthedepthofthetwosubtreesofeverynodenever...

 publicclassTreeNode{publicintval;publicTreeNodeleft;publicTreeNoderight;publicTreeNode(intx){val=x;}}打印代码privatevoidWriteTreeNode(TreeNodenode){StringBuil...

Invertabinarytree.Example:Input:4/27//1369Output:4/72//9631Trivia:ThisproblemwasinspiredbythisoriginaltweetbyMaxHowell:/Google:90%ofourengineersusethesoftwareyo...

Givenabinarysearchtree(BST),findthelowestcommonancestor(LCA)oftwogivennodesintheBST.AccordingtothedefinitionofLCAonWikipedia:“Thelowestcommonancestorisdef...

Givenabinarytree,returnallroot-to-leafpaths.Note: Aleafisanodewithnochildren.Example:Input:1/235Output:["1->2->5","1->3"]Explanation:Allroot-to-le...

Givenabinarysearchtree(BST)withduplicates,findallthe mode(s) (themostfrequentlyoccurredelement)inthegivenBST.AssumeaBSTisdefinedasfollows:Theleftsubtr...

GivenaBinarySearchTree(BST),convertittoaGreaterTreesuchthateverykeyoftheoriginalBSTischangedtotheoriginalkeyplussumofallkeysgreaterthantheoriginalkeyinBST.Examp...

Givenabinarytree,youneedtocomputethelengthofthediameterofthetree.Thediameterofabinarytreeisthelengthofthelongestpathbetweenanytwonodesinatree.Thispathmayormayno...

注：HashMap底层也是用数组，HashSet底层实际上也是HashMap，HashSet类中有HashMap属性（我们如何在API中查属性）。HashSet实际上为(key.null)类型的HashMap。有key值而没有value值。 正因为以上的原因，TreeSet和TreeMap的实现也有些类似的关...

  aliastree='tree--charsetASCII'  ...