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Title Description Determines whether a number n is a happy number. The definition of happy number is as follows: Starting with any positive integer, replace the number by the sum of the squares of its digits. Repeat the process until the number equals 1 (where it will stay), or it loops endlessly in a cycle which does not include 1. Those ...

/** * Definition for a binary tree node. * struct TreeNode { * int val; * TreeNode *left; * TreeNode *right; * TreeNode() : val(0), left(nullptr), right(nullptr) {} * TreeNode(int x) : val(x), left(nullptr), right(nullptr) {} * TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {} ...

1. Judgment Subsequence ( leetcode392) The idea is that we can use violence directly for pattern matching, but if we use violence directly in addition to the kmp algorithm, we do not need to use backtracking, because it is not a continuous substring, but a subsequence, as long as we find the s characters in t and the order is the same, we c ...

1. Force buckle C + + source code class Solution { public: int lengthOfLongestSubstring(string s) { map<char, int> hash; int ans = 0; int i = 0; int n = s.length(); for (int j = 0; j < n; j++) { if (hash.find(s[j]) != hash.end()) { i = max(hash.find(s[j])-> ...

7-5 tribes (20 points) subject In a community, everyone has his own small circle and may belong to many different circles of friends at the same time. We think that all friends of friends are in one tribe, so please count how many disjoint tribes there are in a given community? And check whether any two people belong to the same tribe. Input ...

Command format command [options] [arguments] Basic instructions: Directory related instructions, ordinary file instructions, matching search instructions, permission related instructions Instruction usage rules: instruction name [operation option] [operation object] Instruction Name: the name of a command, indicating the command to be exe ...

Title: Given a string s, reverse the order of characters in each word within a sentence while still preserving whitespace and initial word order. Given a string s, reverse the character order of each word in the sentence while still retaining the spaces and the original word order. Example 1: Input: s = "Let's take LeetCode contest" Output: ...

Title Description Give you an array of rectangles, where rectangles[i] = [xi, yi, ai, bi] represents a rectangle with parallel coordinate axes. The lower left vertex of the rectangle is (xi, yi) and the upper right vertex is (ai, bi). Returns true if all rectangles together exactly cover a rectangular area; Otherwise, false is returned. ...

1. The core of front-end Routing: Change the URL without overall refresh: Implementation methods: 1) hash of URL 2) history of html5 2. hash of URL location.hash=' ' 3. history of HTML5 history.pushState({}, ' ' , 'home' ) history.replaceState({},'','home') pushState() is like entering and exiting the stack. It is a stack structure that ca ...

524. Match the longest word in the dictionary by deleting letters One question per day on September 14, 2021 Title Description Give you a string s and a string array dictionary as a dictionary, find and return the longest string in the dictionary, which can be obtained by deleting some characters in S. If there is more than one answer, the ...