摘要： 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].可用递归，进行。也可以用迭代... 阅读全文

摘要： Given a linked list, determine if it has a cycle in it.Can you solve it without using extra space?每个节点再开辟一个属性存放是否访问过，这样遍历一遍即可知道是否有环。但为了不增加额外的空间，可以设置两个... 阅读全文

摘要： Catalan数令h(1)＝1,h(0)=1，catalan数满足递归式：h(n)= h(1)*h(n-1) + h(2)*h(n-2) + ... + h(n-1)h(1) (其中n>=2)另类递归式： h(n)=((4*n-2)/(n+1))*h(n-1);该递推关系的解为： h(n+1)... 阅读全文

摘要： Givenn, how many structurally uniqueBST's(binary search trees) that store values 1...n?For example,Givenn= 3, there are a total of 5 unique BST's.注意：二... 阅读全文

摘要： 最容易想到的算法是除余法，继而考虑到除法的代价较高，而且除数是2，会想到使用向右移位来代替除法，并使用&0x1操作来取末位的值，这样提高了算法的效率。然而，这样仍然进行了63次&操作、63次移位操作和63次+操作。若假设字长大小不限，记作N，那么上述算法的时间复杂度都为O(N)。具体实现方法：1.除... 阅读全文

摘要： 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 in... 阅读全文

摘要： Related to questionExcel Sheet Column TitleGiven a column title as appear in an Excel sheet, return its corresponding column number.For example:A -> 1... 阅读全文

摘要： I:Say you have an array for which the ith element is the price of a given stock on day i.If you were only permitted to complete at most one transactio... 阅读全文

摘要： 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 an... 阅读全文

摘要： 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 le... 阅读全文