xyqzki的专栏

https://leetcode.com/problems/shortest-palindrome/solution: http://bookshadow.com/weblog/2015/05/22/leetcode-shortest-palindrome/

https://leetcode.com/problems/integer-to-english-words/自己的code，都没有通过。还是判断>99, > 19, >0作为条件。参考http://bookshadow.com/weblog/2015/08/31/leetcode-integer-english-words/

https://leetcode.com/problems/same-tree/我的方法是用dfs来做my code:class Solution(object): def isSameTree(self, p, q): """ :type p: TreeNode :type q: TreeNode :rtype: bool

https://leetcode.com/problems/climbing-stairs/简单的dp思路 d[n] = d[n - 1] + d[n - 2]class Solution(object): def climbStairs(self, n): """ :type n: int :rtype: int """

https://leetcode.com/problems/remove-duplicates-from-sorted-array/思路简单。但是要找对循环点。removeDuplicates2中用j scan所有元素才是最佳方案。 ref: http://www.cnblogs.com/zuoyuan/p/3779816.htmlclass Solution(object): def rem

https://leetcode.com/problems/swap-nodes-in-pairs/没什么技巧。注意不要出错。交换node的操作要仔细。class Solution(object): def swapPairs(self, head): """ :type head: ListNode :rtype: ListNode

https://leetcode.com/problems/longest-common-prefix/class Solution(object): def longestCommonPrefix(self, strs): """ :type strs: List[str] :rtype: str """ if

https://leetcode.com/problems/excel-sheet-column-title/similar question https://leetcode.com/problems/excel-sheet-column-number/使用chr()以及ord()class Solution(object): def convertToTitle(self, n):

https://leetcode.com/problems/maximum-depth-of-binary-tree/recursive的方法最简单class Solution(object): def maxDepth(self, root): """ :type root: TreeNode :rtype: int """

https://leetcode.com/problems/valid-parentheses/要用到stack。 参考http://www.cnblogs.com/zuoyuan/p/3779772.html正确code:class Solution: # @return a boolean def isValid(self, s): stack = []

https://leetcode.com/problems/sort-list/这里又复习了一遍merge list的操作。用归并排序就行参考http://www.cnblogs.com/zuoyuan/p/3699508.htmlclass Solution(object): def mergeList(self, head1, head2): if not head1:

https://leetcode.com/problems/rotate-list/这里思路很简单。但是要注意，k可以大于len(linkedlist). 要求得长度之后取mod。还有就是这个rotate，不需要把rotate部分逆置。 def rotateRight(self, head, k): """ :type head: ListNode

https://leetcode.com/problems/majority-element/import mathclass Solution(object): def majorityElement(self, nums): """ :type nums: List[int] :rtype: int """

https://leetcode.com/problems/count-and-say/重点在理解题意。count and sayclass Solution(object): def countAndSay(self, n): """ :type n: int :rtype: str """ if n == 1

https://leetcode.com/problems/linked-list-cycle/参考http://www.cnblogs.com/zuoyuan/p/3701639.html一开始我错误的code：class Solution(object): def hasCycle(self, head): """ :type head: ListNode

https://leetcode.com/problems/linked-list-cycle-ii/参考http://www.cnblogs.com/zuoyuan/p/3701877.html 有原理解释我的codeclass Solution(object): def detectCycle(self, head): """ :type head: Li

class Solution(object): def flatten(self, root): """ :type root: TreeNode :rtype: void Do not return anything, modify root in-place instead. """ if not root:

https://leetcode.com/problems/partition-list/“穿针引线”法。 构造两个dummy，然后穿针引线。参考http://www.cnblogs.com/zuoyuan/p/3783276.htmlclass Solution(object): def partition(self, head, x): """ :type

https://leetcode.com/problems/reverse-words-in-a-string/class Solution(object): def reverseWords(self, s): """ :type s: str :rtype: str """ return " ".join(s

https://leetcode.com/problems/maximal-square/对于DP的问题，要写state equation, 这里state选择 square length rather than the required area. 这是2D的dp，所以应该是dp[x][y] =?.这里dp[x][y]表示以(x,y)为右下角点的最大square的边长。这里有点不一样的就是，普通

https://leetcode.com/problems/remove-duplicates-from-sorted-list-ii/two pointers链表操作就行class Solution(object): def deleteDuplicates(self, head): """ :type head: ListNode :rty

https://leetcode.com/problems/best-time-to-buy-and-sell-stock-ii/因为可以进行无限次交易，并且在下一次buy之前必须已经sell。所以只需要把所有price曲线价格上涨的部分加起来就行。参考 http://www.cnblogs.com/zuoyuan/p/3765980.htmlclass Solution(object):

如果是sorted arrayhttps://leetcode.com/problems/convert-sorted-array-to-binary-search-tree/ 参考 http://www.cnblogs.com/zuoyuan/p/3722103.html 找到中点，对左右递归就行class Solution(object): def sortedArrayToBST

https://leetcode.com/problems/merge-k-sorted-lists/思路就是把所有的head节点入heap，然后把root，heappop出来。再把被pop出来的node所属于的list的下一个node入heap. 知道heap为空这里要用到heap，python中有heapq.heapify([])这个函数可以对heap进行create，从而进行操作。以及 hea

https://leetcode.com/problems/product-of-array-except-self/由于output[i] = (x0 * x1 * … * xi-1) * (xi+1 * …. * xn-1)因此执行两趟循环：第一趟正向遍历数组，计算x0x_0 ~ xi−1x_{i-1}的乘积第二趟反向遍历数组，计算xi+1x_{i+1} ~ xn−1x_{n-1}的乘积Note

https://leetcode.com/problems/house-robber-ii/注意思路：对于第一个house, 判断其“rob” or “not rob”. if rob, 那么结果就是nums[0] + rob_linear(nums[2:i-1]); if not rob, 结果就是 rob_linear(nums[1:i])参考： http://bookshadow.com/w

https://leetcode.com/problems/game-of-life/参考http://bookshadow.com/weblog/2015/10/04/leetcode-game-life/

https://leetcode.com/problems/permutations/https://leetcode.com/problems/permutations-ii/思路1：递归如果不考虑重复 参考http://www.cnblogs.com/zuoyuan/p/3758816.html http://effyhuang.com/2014/08/06/permutations-lee

backtracking 实际上就是通过DFS策略实现的。看http://blog.youkuaiyun.com/daniel_ustc/article/details/17040315 有模板

https://leetcode.com/problems/minimum-height-trees/有trick 对graph不熟悉。再看几遍。参考http://bookshadow.com/weblog/2015/11/26/leetcode-minimum-height-trees/

https://leetcode.com/problems/best-time-to-buy-and-sell-stock-iv/参考： http://bookshadow.com/weblog/2015/02/18/leetcode-best-time-to-buy-and-sell-stock-iv/ http://www.cnblogs.com/maples7/p/4350047.html

preorder, inorder, postorder的recursive方法还有iterative的方法dfs以及bfsdfs就是pre order枚举所有从root到leaf的path给定一个node，找一条从root到它的path

https://leetcode.com/problems/maximum-subarray/参考http://fisherlei.blogspot.hk/2012/12/leetcode-maximum-subarray.html思路1：假设A(0, i)区间存在k，使得[k, i]区间是以i结尾区间的最大值， 定义为Max[i], 在这里，当求取Max[i+1]时，Max[i+1] = Ma

https://leetcode.com/problems/maximum-product-subarray/参考思路：http://yucoding.blogspot.hk/2014/10/leetcode-quesion-maximum-product.html其实这里与Maximum subarray思路很像，都是dp经典。对max[i]的定义这里与Maximum subarray一致，只是要

https://leetcode.com/problems/combination-sum/这里参照dfs tree2 组合树的建树方法，因为有重合数字，所以子节点不再是只是A[k]后面的元素，子节点应该还是原来所有的元素。例如：参考http://www.cnblogs.com/TenosDoIt/p/3802647.html 比如对于数组3,2,6,7,target = 7,对数组排序得到[2,

http://algorithm.yuanbin.me/zh-cn/GLOSSARY.html#dfs

https://leetcode.com/problems/rotate-image/转置，再每行reverse即可 参考http://www.cnblogs.com/zuoyuan/p/3772978.htmlclass Solution(object): def rotate(self, matrix): """ :type matrix: List[L

https://leetcode.com/problems/generate-parentheses/这里用剩余左括号数目以及剩余右括号数目nl 以及nr来当做输入参数，逐个试探。subres 用 ”字符串来计算。class Solution(object): def dfs(self, nl, nr, subres, res): if nl == 0 and nr == 0:

https://leetcode.com/problems/search-for-a-range/参考 http://www.cnblogs.com/zuoyuan/p/3775904.html思路 就是BS mid找到target之后，再左右搜索边界即可

https://leetcode.com/problems/search-insert-position/思路就是 BS,只要最后记得return low就行参考http://www.cnblogs.com/zuoyuan/p/3772705.html