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catalogue array 1 number of duplicates found 1. hashmap save times   two   Arrays.stream sorting directly query adjacent duplicate 3. set storage (problem solving)   4. Use array index! array 1 number of duplicates found 1. hashmap save times   Use map.get() to determine whether there is one. In fact, you can ou ...

Solution 1 The question is 0108. Convert Sorted Array to Binary Search Tree It is possible to directly use the divide and conquer tree idea of finding the middle position as the root node in the previous question, which is to solve the method of determining the middle position in the linked list. [refer to the official] the method to find the ...

Title: Force bucklehttps://leetcode-cn.com/problems/4sum/ class Solution { public List<List<Integer>> fourSum(int[] nums, int target) { List<List<Integer>> ans = new ArrayList<>(); Arrays.sort(nums); int l; int r; for(int index1=0;index1<nums.length-3;index1++){ ...

Catalog Summary of Today's Brush Topics Single-valued binary tree (easy) The same tree (easy) Prime number calculation position (easy) in binary representation Number (mid)II that occurs only once supplement Summary of Today's Brush Topics Single-valued binary tree (easy) Title link: 965.Single Value Binary Tree-Force Button (leetco ...

All algorithms for breadth and depth traversal of binary tree For the traversal of binary tree, there are two categories: breadth traversal and depth traversal. For depth traversal, it is divided into first order, middle order and second order. These three first, middle and second order can be written by recursive and non recursive algorithms. ...

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Friends of appropriate age People send friend requests to each other. Now given an array containing their age, ages[i] indicates the age of the ith person. When either of the following conditions is met, A cannot send friend requests to B (A, B are not the same person): age[B] <= 0.5 * age[A] + 7 age[B] > age[A] age[B] > 100 && ...

It integrates several writing methods on Li buckle and the writing method of code Capriccio. Thank you! Key points: define the interval clearly and keep it unchanged in the loop operation (loop invariant principle). 1, Number of binary search monotone arrays (no repetition) 1. Left closed right closed int binarySearch(vector<int> &amp ...

T1 17. Print from 1 to the maximum n digits leetcode returns int [] without considering the large number. The original book considers the case that the large number is out of bounds Large number out of bounds is not considered class Solution { public int[] printNumbers(int n) { int m = (int)Math.pow(10,n)-1; //Number of prints to ...

First, give the Activity table used by the four questions: +--------------+---------+ | Column Name | Type | +--------------+---------+ | player_id | int | | device_id | int | | event_date | date | | games_played | int | +--------------+---------+ The primary key of the table is (player_id, event_date). This table s ...