Step-BY-Step

摘要： Given a binary tree, return thepreordertraversal of its nodes' values.For example:Given binary tree{1,#,2,3}, 1 \ 2 / 3return[1,2,3].Note:Recursive solution is trivial, could you do it iteratively?如果不能使用recursive 那么就只能使用stack来保存状态。 1 /** 2 * Definition for binary tree 3 * public clas... 阅读全文

摘要： 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? 1 public class Solution { 2 public ListNode detectCycle(ListNode head) { 3 // IMPORTANT: Please reset any member data you declared, as 4 ... 阅读全文

摘要： Given a linked list, determine if it has a cycle in it.Follow up:Can you solve it without using extra space? 1 public class Solution { 2 public boolean hasCycle(ListNode head) { 3 // IMPORTANT: Please reset any member data you declared, as 4 // the same Solution instance will be ... 阅读全文

摘要： Given a strings, partitionssuch that every substring of the partition is a palindrome.Return the minimum cuts needed for a palindrome partitioning ofs.For example, givens="aab",Return1since the palindrome partitioning["aa","b"]could be produced using 1 cut.这个两个Dp， 一个是对那 阅读全文

摘要： Given a strings, partitionssuch that every substring of the partition is a palindrome.Return all possible palindrome partitioning ofs.For example, givens="aab",Return [ ["aa","b"], ["a","a","b"] ]采用DP来做。为了不重复计算palindrome， 使用一个map 存储从[i,j]是否 阅读全文

摘要： Given a 2D board containing'X'and'O', capture all regions surrounded by'X'.A region is captured by flipping all'O's into'X's in that surrounded region .For example,X X X XX O O XX X O XX O X XAfter running your function, the board should be:X X X XX X X XX X X 阅读全文

摘要： Say you have an array for which theithelement is the price of a given stock on dayi.Design an algorithm to find the maximum profit. You may complete at mosttwotransactions.Note:You may not engage in multiple transactions at the same time (ie, you must sell the stock before you buy again).和前两道题比起来的话， 阅读全文