Dynamic Programming 实际上是[LeetCode] 系统刷题4_Binary Tree & Divide and Conquer的基础上,加上记忆化的过程.就是说,如果这个题目实际上是类似于Divide and conquer或者说是DFS,但是在计算过程中有很多重复计算同样的过程的话,那么就可以用Dynamic prgramming/记忆化搜索来完成.基本就是利用空间来简化时间复杂度的过程. 可以/很有可能使用Dynamic programming的条件,满足之一即可. 1.…
Given a binary tree and a sum, find all root-to-leaf paths where each path's sum equals the given sum. For example:Given the below binary tree and sum = 22, 5 / \ 4 8 / / \ 11 13 4 / \ / \ 7 2 5 1 return [ [5,4,11,2], [5,8,4,5] ] 112. Path Sum 的拓展,上一…
<span style="font-family: Arial, Helvetica, sans-serif; background-color: rgb(255, 255, 255);">leetcode第188题,Best Time to Buy and Sell Stock IV题目如下:</span> https://leetcode.com/problems/best-time-to-buy-and-sell-stock-iv/ Say you hav…
题目:(据说是facebook的面试题哦) The count-and-say sequence is the sequence of integers beginning as follows:1, 11, 21, 1211, 111221, ... 1 is read off as "one 1" or 11.11 is read off as "two 1s" or 21.21 is read off as "one 2, then one 1&qu…
题目难度:Medium 题目: Given an array S of n integers, are there elements a, b, c, and d in S such that a + b + c + d = target? Find all unique quadruplets in the array which gives the sum of target. Note: The solution set must not contain duplicate quadrup…