You are a professional robber planning to rob houses along a street. Each house has a certain amount of money stashed, the only constraint stopping you from robbing each of them is that adjacent houses have security system connected and it will a...
IntersectionOfTwoLinkedLists
Write a program to find the node at which the intersection of two singly linked lists begins. For example, the following two linked lists: A: a1 → a2 ↘ c1 → c2 → c3 ↗ B: b...
LinkedListCycle
Given a linked list, determine if it has a cycle in it. Follow up: Can you solve it without using extra space? 分析 一开始使用了复杂度O(n^2)的方法，使用两个指针a, b。a从表头开始一步一步往前走，遇到null则说明没有环，返回false；a每走一步，b从头开始走，如果遇到b==a.next，则说明有环true，如果遇到b==a，则说明暂时没有环，继续循环。 后来找...
BinaryTreeLevelOrderTraversal树的层序遍历
Given a binary tree, return the level order traversal of its nodes' values. (ie, from left to right, level by level). For example: Given binary tree [3,9,20,null,null,15,7], 3 / \ 9 20 / \ 15 7 return its level order traversa...
SymmetricTree
Given a binary tree, check whether it is a mirror of itself (ie, symmetric around its center). For example, this binary tree [1,2,2,3,4,4,3] is symmetric: 1 / \ 2 2 / \ / \ 3 4 4 3 But the following [1,2,2,null,3,null,3] is not: 1 / \ 2 2...
ValidateBinarySearchTree
import org.junit.jupiter.api.Test;import org.omg.CORBA.INTERNAL; Given a binary tree, determine if it is a valid binary search tree (BST). Assume a BST is defined as follows: The left subtree of a node contains only nodes with keys...
UniqueBinarySearchTreesII
import org.junit.jupiter.api.Test; 题目的描述如下 * Given n, how many structurally unique BST's (binary search trees) that store values 1...n? For example, Given n = 3, there are a total of 5 unique BST's. 1 3 3 2 ...
卡塔兰数列[UniqueBinarySearchTrees]
Given n, how many structurally unique BST’s (binary search trees) that store values 1…n? For example,Given n = 3, there are a total of 5 unique BST’s. 1 3 3 2 1 \ / / / \ \ 3 2 1 ...