Leetcode#117. Populating Next Right Pointers in Each Node II
leetcode116
ProblemGiven a binary tree
1234567struct Node { int val; Node *left; Node *right; Node *next;}
Populate each next pointer to point to its next right node. If there is no next right node, the next pointer should be set to NULL.
Initially, all next pointers are set to NULL.
Example 1:
1234Input: root = [1,2,3,4,5,null,7]Output: [1,#,2,3,#,4,5,7,#]Explanation:Given the above binary tree (Figure A), your function should populate each next pointer to point to its next righ ...
Leetcode#116. Populating Next Right Pointers in Each Node
ProblemYou are given a perfect binary tree where all leaves are on the same level, and every parent has two children. The binary tree has the following definition:
1234567struct Node { int val; Node *left; Node *right; Node *next;}
Populate each next pointer to point to its next right node. If there is no next right node, the next pointer should be set to NULL.
Initially, all next pointers are set to NULL.
Example 1:
1234Input: root = [1,2,3,4,5,6,7]Output: [1,#,2,3,#,4,5,6,7,#]E ...
Leetcode#226. Invert Binary Tree
ProblemGiven the root of a binary tree, invert the tree, and return its root.
Example 1:
123Input: root = [4,2,7,1,3,6,9]Output: [4,7,2,9,6,3,1]
Example 2:
123Input: root = [2,1,3]Output: [2,3,1]
Example 3:
123Input: root = []Output: []
Constraints:
The number of nodes in the tree is in the range [0, 100].
100 <= Node.val <= 100
Solve1234567891011121314151617181920# Definition for a binary tree node.# class TreeNode:# def __init__(self, val=0, left=None, right=None):# se ...
Leetcode#201. Bitwise AND of Numbers Range
ProblemGiven two integers left and right that represent the range [left, right], return the bitwise(位元運算) AND of all numbers in this range, inclusive.
Example 1:
123Input: left = 5, right = 7Output: 4
Example 2:
123Input: left = 0, right = 0Output: 0
Example 3:
123Input: left = 1, right = 2147483647Output: 0
Constraints:
0 <= left <= right <= 2^31 - 1
Solve對區間的數字進行位元運算
12345678根據位元的值（0或1）進行邏輯運算位元 AND（&）：對兩個二進制數進行對應位元的 AND 運算。當兩個對應位元都為1時，結果的對應位元為1，否則為0。10101010 (170)& 1100 ...
Leetcode#121. Best Time to Buy and Sell Stock
ProblemYou are given an array prices where prices[i] is the price of a given stock on the ith day.
You want to maximize your profit by choosing a single day to buy one stock and choosing a different day in the future to sell that stock.
Return the maximum profit you can achieve from this transaction. If you cannot achieve any profit, return 0.
Example 1:
12345Input: prices = [7,1,5,3,6,4]Output: 5Explanation: Buy on day 2 (price = 1) and sell on day 5 (price = 6), profit = 6-1 = 5.Note that buyi ...
改變git推送人與信箱
當你需要更改 Git 中的使用者名稱和電子郵件地址時，可以按照以下步驟執行：
使用以下命令檢視當前的 Git 設定：
12git config --list
這將顯示當前的 Git 設定列表。
使用以下命令設定新的使用者名稱：12git config --global user.name "Name"
將 “Name” 替換為你要設定的新使用者名稱。
使用以下命令設定新的電子郵件地址：
123git config --global user.email "email@example.com"
時間複雜度
時間複雜度由小到大依次為:O(1) < O(logn) < O(n) < O(nlogn) < O(n^2) < O(n^3) < O(2^n) < O(n!) < O(n^n)
時間複雜度
描述
O(1)
常數時間
O(logn)
對數時間
O(n)
線性時間
O(nlogn)
線性對數時間
O(n^2)
平方時間
O(n^3)
立方時間
O(2^n)
指數時間
O(n!)
階乘時間
O(n^n)
階乘時間
常見的時間複雜度O(1)：常數時間123def constant_algo(items): result = items[0] * items[0] print(result)
O(n)：線性時間123def linear_algo(items): for item in items: print(item)
O(n^2)：平方時間1234def quadratic_algo(items): for item in items: ...
Leetcode#23. Merge k Sorted Lists
ProblemYou are given an array of k linked-lists lists, each linked-list is sorted in ascending order.
Merge all the linked-lists into one sorted linked-list and return it.
Example 1:
1234567891011Input: lists = [[1,4,5],[1,3,4],[2,6]]Output: [1,1,2,3,4,4,5,6]Explanation: The linked-lists are:[ 1->4->5, 1->3->4, 2->6]merging them into one sorted list:1->1->2->3->4->4->5->6
Example 2:
123Input: lists = []Output: []
Example 3:
123Input: lists = [[]]Output: [ ...
Leetcode#427. Construct Quad Tree
ProblemGiven a n * n matrix grid of 0's and 1's only. We want to represent grid with a Quad-Tree.
Return the root of the Quad-Tree representing grid.
A Quad-Tree is a tree data structure in which each internal node has exactly four children. Besides, each node has two attributes:
val: True if the node represents a grid of 1’s or False if the node represents a grid of 0’s. Notice that you can assign the val to True or False when isLeaf is False, and both are accepted in the answer.
isLea ...
Leetcode#148. Sort Listk
ProblemGiven the head of a linked list, return the list after sorting it in ascending order.
Example 1:
123Input: head = [4,2,1,3]Output: [1,2,3,4]
Example 2:
123Input: head = [-1,5,3,4,0]Output: [-1,0,3,4,5]
Example 3:
12Input: head = []Output: []
Solve1234567891011121314151617181920212223242526272829303132333435363738394041424344class Solution: def sortList(self, head: Optional[ListNode]) -> Optional[ListNode]: # 沒有 或只只有一個 代表已經排好了 if not head or not head.next: ...