fight_to_dead-CSDN博客

原创 Leetcode Path Sum

题目：Given a binary tree and a sum, determine if the tree has a root-to-leaf path such that adding up all the values along the path equals the given sum.For example:Given the below binary

2015-05-14 22:13:41 313

原创 Leetcode Sum Root to Leaf Numbers

题目：Given a binary tree containing digits from 0-9 only, each root-to-leaf path could represent a number.An example is the root-to-leaf path 1->2->3 which represents the number 123.

2015-05-14 21:55:52 373

原创 Leetcode Binary Tree Right Side View

题目：Given a binary tree, imagine yourself standing on the right side of it, return the values of the nodes you can see ordered from top to bottom.For example:Given the following binary

2015-05-14 11:32:03 283

原创 Leetcode Binary Search Tree Iterator 二叉搜索树迭代器

题目：Implement an iterator over a binary search tree (BST). Your iterator will be initialized with the root node of a BST.Calling next() will return the next smallest number in the BST.

2015-05-14 11:18:19 319

原创 Leetcode Populating Next Right Pointers in Each Node II

题目：Follow up for problem "Populating Next Right Pointers in Each Node".What if the given tree could be any binary tree? Would your previous solution still work?Note:You may only

2015-05-14 10:53:12 244

原创 Leetcode Populating Next Right Pointers in Each Node

题目：Given a binary tree struct TreeLinkNode { TreeLinkNode *left; TreeLinkNode *right; TreeLinkNode *next; }Populate each next pointer to point to its next

2015-05-14 10:41:48 280

原创 Leetcode Minimum Depth of Binary Tree 二叉树最小深度

题目：Given a binary tree, find its minimum depth.The minimum depth is the number of nodes along the shortest path from the root node down to the nearest leaf node.分析：这道题可以和求最大深度一

2015-05-13 17:43:17 314

原创 Leetcode Construct Binary Tree from Inorder and Postorder Traversal 中序后序遍历重组二叉树

题目：Given inorder and postorder traversal of a tree, construct the binary tree.Note:You may assume that duplicates do not exist in the tree.分析：1. 后序遍历的最后一个节点为树的根节点2. 找到根节点在中

2015-05-13 17:00:21 441

原创 Leetcode Construct Binary Tree from Preorder and Inorder Traversal 前序中序遍历重组二叉树

题目：Given preorder and inorder traversal of a tree, construct the binary tree.Note:You may assume that duplicates do not exist in the tree.分析：1. 前序遍历的第一个节点为树的根节点2. 在中序遍历中找到根

2015-05-13 16:29:44 425

原创 Leetcode Single Number

题目：Given an array of integers, every element appears twice except for one. Find that single one.Note:Your algorithm should have a linear run time complexity. Could you implement it wit

2015-05-12 18:19:01 246

原创 Leetcode Balanced Binary Tree 平衡二叉树

题目：Given a binary tree, determine if it is height-balanced.For this problem, a height-balanced binary tree is defined as a binary tree in which the depth of the two subtrees of every nod

2015-05-12 14:55:22 326

原创 Leetcode Convert Sorted Array to Binary Search Tree 有序数组转换成二叉搜索树BST

题目：Given an array where elements are sorted in ascending order, convert it to a height balanced BST.分析：这道题和有序链表转换成BST的方法相同，都是用递归。 1. 递归的结束条件是当start>=end2. 找到数组的中点，作为根节点3. 递归的在左半边构建

2015-05-12 12:20:47 458 1

原创 Leetcode Triangle

题目：Given a triangle, find the minimum path sum from top to bottom. Each step you may move to adjacent numbers on the row below.For example, given the following triangle[ [2],

2015-05-12 11:34:33 250

原创 Leetcode Unique Paths II

题目：Follow up for "Unique Paths":Now consider if some obstacles are added to the grids. How many unique paths would there be?An obstacle and empty space is marked as 1 and 0 respectiv

2015-05-11 22:58:51 239

原创 Leetcode Unique Paths

题目：A robot is located at the top-left corner of a m x n grid (marked 'Start' in the diagram below).The robot can only move either down or right at any point in time. The robot is trying

2015-05-11 22:42:17 241

原创 Leetcode Best Time to Buy and Sell Stock

题目：Say you have an array for which the ith element is the price of a given stock on day i.If you were only permitted to complete at most one transaction (ie, buy one and sell one share o

2015-05-11 22:32:59 302

原创 Leetcode House Robber

题目：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 a

2015-05-11 20:49:59 273

原创 Leetcode Climbing Stairs 爬楼梯

题目：You are climbing a stair case. It takes n steps to reach to the top.Each time you can either climb 1 or 2 steps. In how many distinct ways can you climb to the top?分析：这道题属于动

2015-05-11 20:34:50 305

原创动态规划题目思路

做动态规划题目主要考虑的几个方面：1. 每一个状态的含义，其中蕴含了怎样的小规模问题的结果2. 状态之间的关系，即如何通过小规模的状态计算大规模的状态3. 初始化状态，首先找到最小的问题的状态3. 结果，哪一个状态是最终需要的结果什么情况下想到用动态规划：1. 问题需要求最大/最小2. 求是还是不是3. 找到所有可能的方案4. 不能用排序

2015-05-11 20:24:16 283

原创 Leetcode Binary Tree Postorder Traversal 二叉树后序遍历

题目：Given a binary tree, return the postorder traversal of its nodes' values.For example:Given binary tree {1,#,2,3}, 1 \ 2 / 3return [3,2,1].Note: Re

2015-05-11 19:48:03 269

原创 Leetcode Symmetric Tree 对称二叉树

题目：Given a binary tree, check whether it is a mirror of itself (ie, symmetric around its center).For example, this binary tree is symmetric: 1 / \ 2 2 / \ / \3 4 4 3

2015-05-11 19:10:13 279

原创 Leetcode Binary Tree Inorder Traversal 二叉树中序遍历

题目：Given a binary tree, return the inorder traversal of its nodes' values.For example:Given binary tree {1,#,2,3}, 1 \ 2 / 3return [1,3,2].Note: Recu

2015-05-11 18:54:48 247

原创 Leetcode Binary Tree Preorder Traversal 二叉树先序遍历

题目：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: Rec

2015-05-11 17:18:54 297

原创 Leetcode Binary Tree Zigzag Level Order Traversal

题目：Given a binary tree, return the zigzag level order traversal of its nodes' values. (ie, from left to right, then right to left for the next level and alternate between).For example:

2015-05-11 15:13:49 254

原创 Leetcode Binary Tree Level Order Traversal II 二叉树分层遍历

题目：Given a binary tree, return the bottom-up level order traversal of its nodes' values. (ie, from left to right, level by level from leaf to root).For example:Given binary tree {3,9,2

2015-05-11 14:16:41 251

原创 Leetcode Binary Tree Level Order Traversal 二叉树分层遍历

题目：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,#,#,15,7}, 3 / \

2015-05-11 14:07:00 289

原创 Leetcode Maximum Depth of Binary Tree 二叉树最大深度

题目：Given a binary tree, find its maximum depth.The maximum depth is the number of nodes along the longest path from the root node down to the farthest leaf node.分析：递归的向下找，取左右子

2015-05-11 12:06:15 340

原创 Leetcode Same Tree 判断两棵二叉树是否相同

题目：Given two binary trees, write a function to check if they are equal or not.Two binary trees are considered equal if they are structurally identical and the nodes have the same value.

2015-05-11 11:53:57 558

原创 Leetcode Sort List 链表排序

题目：Sort a linked list in O(n log n) time using constant space complexity.分析：选择用归并排序来解决。但是找中点的时候需要注意对于 1 --> 2 --> null 的情况，我们需要mid为1，才能把1和2分开，找中点的时候让fast先走一步即可。1. 如果链表为空或只有一个节点

2015-05-11 11:19:03 235

原创 Leetcode Reverse Nodes in k-Group

题目：Given a linked list, reverse the nodes of a linked list k at a time and return its modified list.If the number of nodes is not a multiple of k then left-out nodes in the end should re

2015-05-10 16:00:47 206

原创 Leetcode Reorder List 链表重排序

题目：Given a singly linked list L: L0→L1→…→Ln-1→Ln,reorder it to: L0→Ln→L1→Ln-1→L2→Ln-2→…You must do this in-place without altering the nodes' values.For example,Given {1,2,3,4}, r

2015-05-10 11:42:39 311

原创 Leetcode Convert Sorted List to Binary Search Tree 把有序链表转换成二叉搜索树

题目：Given a singly linked list where elements are sorted in ascending order, convert it to a height balanced BST.分析：举一个例子，假如链表为 1--> 2 --> 3 --> 4 --> 5 --> 6 --> 7。根据二叉搜索树的性质 root.va

2015-05-10 10:13:49 420

原创 Leetcode Rotate List 旋转链表

题目：Given a list, rotate the list to the right by k places, where k is non-negative.For example:Given 1->2->3->4->5->NULL and k = 2,return 4->5->1->2->3->NULL.分析：1. k的值可能大于链

2015-05-09 14:31:15 364

原创 Leetcode Merge k Sorted Lists 合并k个链表

题目：Merge k sorted linked lists and return it as one sorted list. Analyze and describe its complexity.分析：1. 用暴力的方法一个一个合并链表会超时，分析所需要的时间复杂度：假设链表的长度为n，每两个链表合并所需要的时间为n+n，k个链表一共需要合并k

2015-05-09 14:03:05 345

原创 Leetcode Swap Nodes in Pairs 交换链表的节点对

题目：Given a linked list, swap every two adjacent nodes and return its head.For example,Given 1->2->3->4, you should return the list as 2->1->4->3.Your algorithm should use only cons

2015-05-08 20:43:48 281

原创 Leetcode Remove Nth Node From End of List 删除链表倒数第n个元素

题目：Given a linked list, remove the nth node from the end of list and return its head.For example, Given linked list: 1->2->3->4->5, and n = 2. After removing the second node from

2015-05-08 18:41:56 276

原创 Leetcode Copy List with Random Pointer 拷贝链表

题目：A linked list is given such that each node contains an additional random pointer which could point to any node in the list or null.Return a deep copy of the list.分析：1. 遍历链表，

2015-05-08 17:02:46 270

原创 Leetcode Linked List Cycle II 循环链表入口

题目：Given a linked list, return the node where the cycle begins. If there is no cycle, return null.分析：个人觉得这题的原理没有必要一定用数学公式深究，记住这个方法就可以，因为对别的题并不具备推广性，有兴趣的话网上的数学推导也有很多。1. 首先利用快慢

2015-05-08 15:39:32 306

原创 Leetcode Partition List 分割链表

题目：Given a linked list and a value x, partition it such that all nodes less than x come before nodes greater than or equal to x.You should preserve the original relative order of the nod

2015-05-07 21:38:59 433

原创 Leetcode Add Two Numbers 两个链表表示的数相加

题目：You are given two linked lists representing two non-negative numbers. The digits are stored in reverse order and each of their nodes contain a single digit. Add the two numbers and return

2015-05-07 20:00:07 457

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