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36. Valid Sudoku Determine if a 9 x 9 Sudoku board is valid. Only the filled cells need to be validated according to the following rules: Each row must contain the digits 1-9 without repetition. Each column must contain the digits 1-9 without repetition. Each of the nine 3 x 3 sub-boxes of the grid must contain the digits 1-9 without repetition. Note: A Sudoku board (partially filled) could be v..

Question: You are given an integer array height of length n. There are n vertical lines drawn such that the two endpoints of the ith line are (i, 0) and (i, height[i]). Find two lines that together with the x-axis form a container, such that the container contains the most water. Return the maximum amount of water a container can store. Notice that you may not slant the container. Example 1: Inp..

Hash Tables A data structure that maps keys to values for highly efficient lookup. 1. Compute the key's hash code, usually an int or long. Note that two different keys could have the same hash code, as there may be an infinite number of keys and a finite number of ints 2. Then, map the hash code to an index in the array. This could be done with something like hash(key) % array_length. Two differ..

Example: Print all positive integer solutions to the equation a^3 + b^3 = c^3 + d^3 and a, b, c, d are integers between 1 and 1000. 1. A brute force solutions n = 1000 n = 1000 for a from 1 to n for b from 1 to n for c from 1 to n for d from 1 to n if a^3 + b^3 = c^3 + d^3 print a, b, c, d This returns O(n^4) To optimize it we can make a break when we find it n = 1000 for a from 1 to n for b fro..

Joi.array().items() accepts another Joi schema to use against the array elements. So an array of strings is this easy: Joi.array().items(Joi.string()) Same for an array of objects; just pass an object schema to items(): Joi.array().items(Joi.object({ // Object schema }))