取法于道的博客

描述 Given an array of integers, every element appears three times except for one, which appears exactly once. Find that single one. Note: Your algorithm should have a linear runtime complexity. Co...

描述 Find the contiguous subarray within an array (containing at least one number) which has the largest product. For example, given the array [2,3,-2,4], the contiguous subarray [2,3] has the larg...

描述 Given an input string, reverse the string word by word. For example, Given s = “the sky is blue”, return “blue is sky the”. Update (2015-02-12): For C programmers: Try to solve it in-place ...

描述 Evaluate the value of an arithmetic expression in Reverse Polish Notation. Valid operators are +, -, *, /. Each operand may be an integer or another expression. Some examples: ["2", "1", "+...

描述 Sort a linked list in O(n log n) time using constant space complexity. 思路 排序算法有很多，对链表进行排序可以选择比较容易操作的算法，这里选择快速排序法，因为快速排序法比较容易用链表实现。快速排序法的思想：对未排序链表进行遍历，每次找出最小的元素位置，将最小的元素与未排序的第一个元素进行交换，继续遍历，知道所有的元...

描述 Sort a linked list using insertion sort. 思路 首先要明白直接插入排序的概念：遍历一个数组，当找到一个数a，该数比前一个数更小，则将a之前的所有大于a的数全部向前移动1，将a插入最后一个大于该数的位置。用数组排序的代码如下 代码（c#) public void InsertSort(int[] arr) { ...

描述 Given a singly linked list L: L0→L1→…→Ln-1→Ln, reorder it to: L0→Ln→L1→Ln-1→L2→Ln-2→… You must do this in-place without altering the nodes’ values. For example, Given {1,2,3,4}, reorder it t...

描述 Given a binary tree, return the preorder traversal of its nodes’ values. For example: Given binary tree [1,null,2,3], 1 \ 2 / 3 return [1,2,3]. Note: Recursive solution i...

描述 Given a linked list, return the node where the cycle begins. If there is no cycle, return null. Note: Do not modify the linked list. Follow up: Can you solve it without using extra space? 思...

描述 Given a non-empty string s and a dictionary wordDict containing a list of non-empty words, determine if s can be segmented into a space-separated sequence of one or more dictionary words. You may...

描述 Suppose an array sorted in ascending order is rotated at some pivot unknown to you beforehand. (i.e., 0 1 2 4 5 6 7 might become 4 5 6 7 0 1 2). Find the minimum element. You may assume no du...