greyfreedom的专栏

Given a 2D board and a word, find if the word exists in the grid.The word can be constructed from letters of sequentially adjacent cell, where “adjacent” cells are those horizontally or vertically

暂做笔记，以后再详细整理。一、插入排序1、直接插入排序public class InsertSort { public static void insertSort(int[] nums) { int size = nums.length; for (int i = 1; i < size; i++) { if

There are N gas stations along a circular route, where the amount of gas at station i is gas[i].You have a car with an unlimited gas tank and it costs cost[i] of gas to travel from station i to

One way to serialize a binary tree is to use pre-order traversal. When we encounter a non-null node, we record the node’s value. If it is a null node, we record using a sentinel value such as #.

Follow up for H-Index: What if the citations array is sorted in ascending order? Could you optimize your algorithm?Hint:Expected runtime complexity is in O(log n) and the input is sorted.

二叉树的三种遍历方式包括：前序遍历中序遍历后序遍历三种遍历的递归方法都非常好实现，而且简单易懂。非递归实现也是通过使用栈来模拟遍历的过程。顺便提一句，能用递归做的，基本都能用栈来实现。前序遍历和中序遍历的非递归写法相对比较简单，只需要模拟遍历过程即可。后序遍历非递归写法比较难，需要借助一个辅助指针来记录右子树是否访问过，以防止重复访问陷入死循环。下面分别给出三种遍历方法的递归和非递

第一题在一组数的编码中，若任意两个相邻的代码只有一位二进制数不同， 则称这种编码为格雷码(Gray Code)，请编写一个函数，使用递归的方法生成N位的格雷码。给定一个整数n，请返回n位的格雷码，顺序为从0开始。测试样例：1返回：["0","1"]题解：该题考察格雷码生成规则。具体思想参考我的另一篇博文。本题注意以下几点：1、要求返回的是字符

The gray code is a binary numeral system where two successive values differ in only one bit.Given a non-negative integer n representing the total number of bits in the code, print the sequence of

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:"((()))", "(()())", "(())()", "()(())", "()

Given a string array words, find the maximum value of length(word[i]) * length(word[j]) where the two words do not share common letters. You may assume that each word will contain only lower case

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].Note: Recursive solution is

最近在看程序员面试金典，在链表部分看到有一题问如何判断链表是否是回文串，然后想到白书中也有对最长回文子串的讨论，故想做一点总结。一、判断链表是否为回文串链表的数据结构是这样子滴：public class Node { public int val; public Node next; public Node(int val) {