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摘要： Determine if a 9x9 Sudoku board is valid. Only the filled cells need to be validated according to the following rules: 1. Each row must contain the digits 1-9 without repetition. 2. Each column mu... 阅读全文

摘要： public class Employee{ static double bonusRate = 0.1; final String name; final String id; int age; int salary; int level; Employee(String name, int age, String id, int le... 阅读全文

摘要： ood Take it slow , if you understand it, u don’t have to memorize it. The more you understand a thing , the less you need to memorize it Odd standard 阅读全文

摘要： Given two integers representing the numerator and denominator of a fraction, return the fraction in string format. If the fractional part is repeating 阅读全文

摘要： https://medium.baqend.com/nosql-databases-a-survey-and-decision-guidance-ea7823a822d What are horizontal and vertical partitions in database and what 阅读全文

摘要： 535. Encode and Decode TinyURL Note: This is a companion problem to the System Design problem: Design TinyURL. TinyURL is a URL shortening service where you enter a URL such as https://leetcode.com/... 阅读全文

摘要： 需要把这道题从brute force 分析， 然后找到重复的计算， 然后一步步优化， 一直到 一维dp. 分析时间复杂度 https://www.youtube.com/watch?v=_MYkrCfFb4M LeetCode wants to give one of its best employees the option to travel among N cities to c... 阅读全文

摘要： In a row of trees, the i-th tree produces fruit with type tree[i]. You start at any tree of your choice, then repeatedly perform the following steps: 1. Add one piece of fruit from this tree to your ... 阅读全文

摘要： In the "100 game," two players take turns adding, to a running total, any integer from 1..10. The player who first causes the running total to reach or exceed 100 wins. What if we change the game so ... 阅读全文

摘要： There are N workers. The i-th worker has a quality[i] and a minimum wage expectation wage[i]. Now we want to hire exactly K workers to form a paid group. When hiring a group of K workers, we must ... 阅读全文

摘要： 看不懂 union find 的代码 https://leetcode.com/problems/bricks-falling-when-hit/discuss/141229/JAVA-Simple-DFS-16ms-reversely-add-bricks-back Very clever idea using -1 to stop visiting the points already ... 阅读全文

摘要： https://www.youtube.com/watch?v=g5wLHFTodm0 https://leetcode.com/problems/predict-the-winner/solution/ https://www.cnblogs.com/liujinhong/p/6477367.ht 阅读全文

摘要： Given an unsorted integer array, find the smallest missing positive integer. Example 1: Input: [1,2,0] Output: 3 Example 2: Input: [3,4,-1,1] Output: 阅读全文

摘要： it teaches you in the real world. Programmers are always been ask to deal with dirty works. Besides detail-oriented mindset, I think this question als 阅读全文

摘要： https://www.youtube.com/watch?v=8Kd-Tn_Rz7s Java有TreeMap和TreeSet。 阅读全文

摘要： There are N gas stations along a circular route, where the amount of gas at station i is gas[i]. You have a car with an unlimited gas tank and it cost 阅读全文

摘要： https://leetcode.com/problems/count-complete-tree-nodes/discuss/61958/Concise-Java-solutions-O(log(n)2) 阅读全文

摘要： (3)找出1-650中所有的ambiguous number,定义：如果把一个数upside down还是一个有效数的话，这个数就是ambiguous，比如19 -> 61, follow up找到1-n中的这种数 A strobogrammatic number is a number that looks the same when rotated 180 degrees (look... 阅读全文

摘要： Assume you have an array of length n initialized with all 0's and are given k update operations. Each operation is represented as a triplet: [startIndex, endIndex, inc] which increments each element ... 阅读全文

摘要： https://leetcode.com/problems/find-k-pairs-with-smallest-sums/discuss/84551/simple-Java-O(KlogK)-solution-with-explanation public class Solution { public List kSmallestPairs(int[] nums1, int[... 阅读全文