给的多叉树, 找这颗树里面最长的路径长度 解法就是在子树里面找最大的两个(或一个,如果只有一个子树的话)高度加起来. 对于每一个treenode, 维护它的最高的高度和第二高的高度,经过该点的最大路径就是:  最高高度+第二高高度,然后return 最高高度 package fbPractise; import java.util.*; class TreeNode { int val; List<TreeNode> children; public TreeNode(int value) {…

给一个 二叉树 , 求最深节点的最小公共父节点 . retrun . 先用 recursive , 很快写出来了, 要求用 iterative . 时间不够了... Recursion: 返回的时候返回lca和depth,每个node如果有大于一个子节点的depth相同就返回这个node,如果有一个子节点depth更深就返回个子节点lca,这个o(n)就可以了 Iteration: tree的recursion换成iteration处理,一般用stack都能解决吧(相当于手动用stack模拟re…

We know that the longest path problem for general case belongs to the NP-hard category, so there is no known polynomial time solution for it. However, for a special case which is directed acyclic graph, we can solve this problem in linear time. First…

We all know that the shortest path problem has optimal substructure. The reasoning is like below: Supppose we have a path p from node u to v, another node t lies on path p: u->t->v ("->" means a path). We claim that u->t is also a sh…

转自:Pavel's Blog Now let's say we want to find the LCA for nodes 4 and 9, we will need to traverse the whole tree to compare each node so that we can locate the nodes. Now considering that we start the traversal with the left branch (pre-order travers…

版权声明:欢迎查看本博客.希望对你有有所帮助 https://blog.csdn.net/cqs_2012/article/details/24880735 the longest distance of a binary tree 个人信息:就读于燕大本科软件project专业 眼下大三; 本人博客:google搜索"cqs_2012"就可以; 个人爱好:酷爱数据结构和算法,希望将来从事算法工作为人民作出自己的贡献; 博客内容:the longest distance of a bi…

Given a string, calculate how many substring is palindrome. Ignore non-char characters. Ignore case; Ex: "A@,b123a", equals "Aba", should output 4: "A", "b", "a", "Aba" Spread from center: Like L…

tasks has cooldown time, give an input task id array, output finish time input: AABCA A--ABCA output:7 package fb; import java.util.*; public class Scheduler { public int task(int[] tasks, int cooldown) { int time = 0; HashMap<Integer, Integer> map…

数unique island, 比如 110000 110001 001101 101100 100000 总共两个unique岛,不是四个 方法可以是记录每次新的岛屿搜索的路径,left,right,up,down, 作为标志是否相同的key,存hashset package fbOnsite; import java.util.*; public class UniqueIsland { public int countIsland(int[][] grid) { HashSet<Strin…

给一组括号,remove最少的括号使得它valid 从左从右各scan一次 package fb; public class removeParen { public static String fix(String str) { StringBuffer res = new StringBuffer(str); int l = 0, r = 0; int i = 0; while (i < res.length()) { if (res.charAt(i) == '(') l++; else…