剑指 Offer 09. 用两个栈实现队列题目来源：力扣（LeetCode）https://leetcode-cn.com/problems/yong-liang-ge-zhan-shi-xian-dui-lie-lcof题目用两个栈实现一个队列。队列的声明如下，请实现它的两个函数 appendTail 和 deleteHead ，分别完成在队列尾部插入整数和在队列头部删除整数的功能。(若队列中没有元素，deleteHead 操作返回 -1 )示例 1：输入：
["CQueue","appendTail","deleteHead","deleteHead"]
[[],[3],[],[]]
输出：...
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 the end, the linked list becomes 1->2->3->5.
Note:
Given n will always be valid.Try to do this in one pass.这道题目最直接的想法是先把整个list走一遍知道长度，然后再走 用总长度减去所要的点，得到位置就跳过。这样需要走两边...
原题地址：https://oj.leetcode.com/problems/merge-two-sorted-lists/题意：Merge two sorted linked lists and return it as a new list. The new list should be made by splicing together the nodes of the first two lists.解题思路：合并两个已经排好序的链表。代码：# Definition for singly-linked list.
# class ListNode:
# def __init__(self, x):
# self.val = x
# self.next = Noneclass Soluti...
1、类中递归调用添加self；2、root为None，返回03、root不为None，root左右孩子为None，返回14、返回l和r最小深度，l和r初始为极大值； 1# Definition for a binary tree node 2# class TreeNode: 3# def __init__(self, x): 4# self.val = x 5# self.left = None 6# self.right = None 7 8class Solution:9# @param root, a tree node10# @return an integer11def minDepth(self, root):
12if root ...
题目：给定一个链表，每个节点包含一个额外增加的随机指针，该指针可以指向链表中的任何节点或空节点。要求返回这个链表的 深拷贝。 我们用一个由 n 个节点组成的链表来表示输入/输出中的链表。每个节点用一个 [val, random_index] 表示：val：一个表示 Node.val 的整数。random_index：随机指针指向的节点索引（范围从 0 到 n-1）；如果不指向任何节点，则为 null 。思路：先使用哈希表来构建一个新的链表，然后对这个链表赋予ne...
Given a n-ary 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.For example, given a 3-ary tree: We should return its max depth, which is 3. Solution:"""
# Definition for a Node.
class Node(object):def __init__(self, val, children):self.val = valself.children = children
"""class Solution(object):# DFSdef ...
原题地址：https://oj.leetcode.com/problems/largest-rectangle-in-histogram/题意：Given n non-negative integers representing the histogram‘s bar height where the width of each bar is 1, find the area of largest rectangle in the histogram.Above is a histogram where width of each bar is 1, given height = [2,1,5,6,2,3]. The largest rectangle is shown in the shaded area, which has area = 10 unit. For e...
原题地址：https://oj.leetcode.com/problems/find-minimum-in-rotated-sorted-array/解题思路：话说leetcode上面的二分查找题目真的不少啊。下图是这道题的数组的两种情况，分别去处理就可以了。 class Solution:# @param num, a list of integer# @return an integerdef findMin(self, num):L = 0; R = len(num)-1while L < R and num[L] > num[R]:M = (L+R)/2if num[M] < num[R]:R = Melse:L = M+1return num[L] 原文：http://w...
LeetCode 0700. Search in a Binary Search Tree二叉搜索树中的搜索【Easy】【Python】【二叉树】ProblemLeetCodeGiven the root node of a binary search tree (BST) and a value. You need to find the node in the BST that the node‘s value equals the given value. Return the subtree rooted with that node. If such node doesn‘t exist, you should return NULL.For example,Given the tree:4/ 2 7/ 1 3A...
题目来源： https://leetcode.com/problems/best-time-to-buy-and-sell-stock-ii/ 题意分析： 和上题类似，给定array，代表第i天物品i的价格。如果可以交易无数次（手上有物品不能买），问最高利润。 题目思路： 记录当前最小值，如果遇到array[i] < min，那么加上当前的最大值；更新min。 代码（python）：class Solution(object):def maxProfit(self, prices):""":type prices: List[int]:rtype: int"""if len(prices)...
【python】Leetcode每日一题-删除排序链表中的重复元素【题目描述】给你一个链表的头节点 head ，旋转链表，将链表每个节点向右移动 k 个位置。示例1：输入：head = [1,2,3,4,5], k = 2
输出：[4,5,1,2,3]
示例2：输入：head = [0,1,2], k = 4
输出：[2,0,1]
提示：链表中节点的数目在范围 [0, 500] 内
-100 <= Node.val <= 100
0 <= k <= 2 * 10^9
【分析】思路由于 $ 0 \le k \le 2 * 10^9$ ，k较大，因此需要先求出链表总长度，...
Climbing StairsYou 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?python code：class Solution: # @param {integer} n # @return {integer} def climbStairs(self, n): if n<=0: #illegal input return 0 else: if...
Problem:
Given an array and a value, remove all instances of that value in place and return the new length.
The order of elements can be changed. It doesn‘t matter what you leave beyond the new length.Solution:和26题一样，就是判断条件不一样而已。题目大意：给一个数组，要求返回删除所有指定元素的数组。好鸡冻，第一次全部通过，没有一个错误（虽然题目比较简单）。。。。。。贴图留念：Java源代码（248ms）：...
LeetCode 面试题03. 数组中重复的数字【剑指Offer】【Easy】【Python】【数组】【哈希表】【排序】问题力扣找出数组中重复的数字。在一个长度为 n 的数组 nums 里的所有数字都在 0～n-1 的范围内。数组中某些数字是重复的，但不知道有几个数字重复了，也不知道每个数字重复了几次。请找出数组中任意一个重复的数字。示例 1：输入：
[2, 3, 1, 0, 2, 5, 3]
输出：2 或 3 限制：2 <= n <= 100000思路解法一哈希表遍历数组，未出现过的...
最小栈 设计一个支持 push，pop，top 操作，并能在常数时间内检索到最小元素的栈。push(x)?-- 将元素 x 推入栈中。pop()?-- 删除栈顶的元素。top()?-- 获取栈顶元素。getMin() -- 检索栈中的最小元素。Python语言：使用辅助栈记录小的元素class MinStack:def __init__(self):"""initialize your data structure here."""self.stack=[]self.minstack=[]self.length = 0def push(self, x: int) -> None:self.stack.append(x)if se...
1 'B' -&' />
题目：
解码方法：一条包含字母 A-Z 的消息通过以下方式进行了编码：? 'A' -> 1 'B' -> 2 ... 'Z' -> 26 给定一个只包含数字的非空字符串，请计算解码方法的总数。??
思路：
一开始理解错题目了，使用字典去对应，发现题目要求不是这样的。
之后使用动态规划来做，需要考虑的情况比较多，踩了很多坑。
程序：
class?Solution:
????def?numDecodings(self,?s:?str)?->?int:
????????if?not?s:
????????????return?0
????????if?s[0]?==?'0':
????????????return?0
????????length?=?len(s)
????????counter?=?1
????????auxiliary_counter?=?1
????????if?int(s)?<=?10:
????????????return?1
????????elif?10?<?int(s)?<=?26:
????????????if?int(s)?==?20:
????????????????return?1
????????????else:
????????????????return?2
????????else:
????????????for?index?in?range(1,?length):
????????????????if?s[index]?==?'0':
????????????????????if?s[index?-?1]?==?'1'?or?s[index?-?1]?==?'2':
????????????????????????counter?=?auxiliary_counter
????????????????????else:
????????????????????????return?0
????????????????else:
????????????????????if?s[index?-?1]?==?'1'??or?(s[index?-?1]?==?'2'?and?'1'?<=?s[index]?<=?'6'):
????????????????????????auxiliary?=?counter
????????????????????????counter?+=?auxiliary_counter
????????????????????????auxiliary_counter?=?auxiliary
????????????????????else:
????????????????????????auxiliary_counter?=?counter
????????return?counter