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preface: ·The depth first traversal and width first traversal of binary tree are the basis for solving the problem of binary tree. Mastering the common traversal methods of binary tree can make us solve the problem of binary tree more handy. catalogue preface: Recursive form of pre -, middle - and post order traversal of binar ...

⭐ New pit in winter vacation -- daily question notes of code Fox 5993. Multiply the value found by 2-week question 1 Give you an integer array nums, and give you an integer original, which is the first number to search in nums. Next, you need to follow the following steps: If the original is found in nums, multiply the original by 2 to g ...

Simple learning notes of search algorithm 1. Algorithm interpretation Common first search algorithms: depth first search (DFS) and breadth first search (BFS), which are widely searched in structures such as graphs and trees Summary: DFS is to catch a matching element and recurse wildly until it does not meet the conditions, requiring auxili ...

344,Reverse string Write a function that inverts the input string. The input string is given as a character array s. Do not allocate additional space to another array. You must modify the input array in place and use the additional space of O(1) to solve this problem.   class Solution { public void reverseString(char[] s) { ...

Sword finger Offer 41 Median in data stream It's really a difficult question 😂, It's really a little difficult. At first, I thought it was violent. I always use sort every time I ask for mid, but as we all know, the time complexity of sort is \ (O(nlogn) \), and it will call mid multiple times, so this method is not used here. In addition, yo ...

Question C is really a little thrilling. It's almost 1:57. There are only three or four minutes left A. Fair Playoff meaning of the title Give the ability values of a,b, C and D, and then a,b, C and D. the winner will enter the finals. Ask whether the two players in the finals have the greatest ability. Is it fair or not analysis Well, yo ...

Sum of K numbers Title Description: give you an array composed of any N numbers. Given a target value target, it is required to find K numbers so that the sum of these K numbers is target. It is required to output the combination of all k digits that meet this condition, and the combination shall not be repeated (take K=4 as an example) I ...

Sorting concept Before sorting, you should first introduce some concepts of sorting: Sorting: it refers to the ascending or descending arrangement of a string of records according to the size of one or some keywords. Stability: it is assumed that there are multiple records with the same keyword in the record sequence to be sorted. If they ...

Segment tree of advanced data structure 1. Prefix and Given an array arr, the array can be very large. During the running of the program, you may have to do several query and update operations: query(arr, L, R) means to calculate the sum of all numbers from subscript L to subscript r in the array arr. update(arr, i, val) means to change the n ...

catalogue 1, Understand the background of the eight queens problem (the eight queens problem Baidu Encyclopedia) 2, General idea 3, Analyze key details IV. labeling 1, Understand the background of the eight queens problem( Eight queens problem_ Baidu Encyclopedia) in short: At 8 × Eight queens are placed on the 8-grid chess so tha ...